Refactor STM8 documentation

2026-01-11 18:33:16 +01:00 · 2016-06-23 10:31:01 +02:00
parent 969e7fa165
commit ee591c7a51
4 changed files with 53 additions and 590 deletions
--- a/ports/stm8/README-COSMIC
+++ b/ports/stm8/README-COSMIC
@@ -13,44 +13,10 @@ This folder contains a port of the Atomthreads real time kernel for the
 STM8 processor architecture. These instructions cover usage of Atomthreads
 with the Cosmic compiler (CXSTM8).
-All of the cross-platform kernel code is contained in the top-level 
+Compiler-agnostic aspects of the usage of Atomthreads can be found in README.
 'kernel' folder, while ports to specific CPU architectures are contained in
 the 'ports' folder tree. A port to a CPU architecture can comprise just one
 or two modules which provide the architecture-specific functionality, such
 as the context-switch routine which saves and restores processor registers
 on a thread switch. In this case, the kernel port is split into two files:
- * atomport.c: Those functions which can be written in C
+Instructions for users of the other compilers are available in README-SDCC,
- * atomport-asm-cosmic.s: The main register save/restore assembler routines
+README-IAR and README-RAISONANCE.
 Each Atomthreads port requires also a header file which describes various
 architecture-specific details such as appropriate types for 8-bit, 16-bit
 etc variables, the port's system tick frequency, and macros for performing
 interrupt lockouts / critical sections:
 * atomport.h: Port-specific header required by the kernel for each port
 A few additional source files are also included here:
 * tests-main.c: Main application file (used for launching automated tests)
 * stm8_interrupt_vector.c: List of interrupt handlers for vector table
 * uart.c: UART wrapper to allow use of stdio/printf()
 * stm8s-periphs/*.*: Peripheral drivers as delivered by ST (no changes
     to distributed code).
 Atomthreads includes a suite of automated tests which prove the key OS
 functionality, and can be used with any architecture ports. This port
 provides an easy mechanism for building, downloading and running the test
 suite to prove the OS on your target.
 The port was carried out and tested on an STM8S105C6 running within an
 STM8S-Discovery board, and supports the Cosmic, Raisonance and IAR compiler
 tools. It is possible to use it with other processors in the STM8 range, as
 well as other hardware platforms and compilers, with minimal changes.
 Platform and compiler specific code has been kept to an absolute minimum.
 This README covers usage of Atomthreads with the Cosmic compiler.
 Instructions for users of the other compilers are available in README-IAR
 and README-RAISONANCE.
 ---------------------------------------------------------------------------
@@ -212,49 +178,6 @@ device and start it running.
 Other programming tools may exist but are not apparent in the toolset
 delivered for use the STM8S Discovery platform.
 ---------------------------------------------------------------------------
 STM8S-DISCOVERY SPECIFICS
 There are very minimal board-specific aspects to the STM8 port so it is
 trivial to run Atomthreads on other STM8 platforms.
 The test applications make use of a LED to indicate test pass/fail status.
 This is currently configured to use a bit in GPIOD, which on the Discovery
 board maps to the board's only LED. You may change the port and register
 bit in tests-main.c to utilise a different pin on other hardware platforms.
 You may also completely omit the LED flashing in the test application if
 you prefer to use the UART for monitoring test status.
 The test applications also make use of the UART to print out pass/fail
 indications and other information. For this you should connect a serial
 cable to the Discovery board via the external pin connectors. Use of
 a UART is not required if you prefer to use the LED or some other method
 of notifying test pass/fail status.
 To connect a serial cable to the Discovery you will need to connect to
 the following pins on the external connectors:
 Vcc: CN2 pin 8
 GND: CN2 pin 7
 UART RX: CN4 pin 11 (connect to TX at the PC end)
 UART TX: CN4 pin 10 (connect to RX at the PC end)
 Note that the board uses TTL levels so you may need to use a level
 converter. External level converters may need to be powered using
 a Vdd of 5v, which can be achieved by positioning JP1 on the Discovery.
 The STM8 device on the Discovery only offers UART2. If you are using a
 different device or wish to use an alternative UART then you must change
 the stm8s_conf.h file.
 If you are using a CPU other than the STM8S105C6 you should change the
 PART macro from "STM8S105" to your target CPU. This can be changed in the
 cosmic.mak Makefile. If you are using the STVD project it should be
 changed in the project preprocessor settings for both Debug and Release
 builds. You may also wish to enable any CPU peripherals which you wish to
 use in the stm8s_conf.h file.
 ---------------------------------------------------------------------------
 RUNNING THE AUTOMATED TESTS
@@ -322,155 +245,6 @@ both Debug and Release builds as follows:
  0x7BF for application usage, and 0x7C0 to 0x7FF for startup stack.
 ---------------------------------------------------------------------------
 RAM FOOTPRINT & STACK USAGE
 The Atomthreads kernel is written in well-structured pure C which is highly
 portable and not targeted at any particular compiler or CPU architecture.
 For this reason it is not highly optimised for the STM8 architecture, and
 by its nature will likely have a higher text and data footprint than an
 RTOS targeted at the STM8 architecture only. The emphasis here is on
 C-based portable, readable and maintainable code which can run on any CPU
 architecture, from the 8-bitters up.
 A good rule of thumb when using Atomthreads on the STM8 architecture is
 that a minimum of 1KB RAM is required in order to support an application
 with 4 or 5 threads and the idle thread. If a minimum of approximately
 128 bytes per thread stack is acceptable then you will benefit from the
 easy-to-read, portable implementation of an RTOS herein.
 The major consumer of RAM when using Atomthreads is your thread stacks.
 Functionality that is shared between several kernel modules is farmed out
 to separate functions, resulting in readable and maintainable code but
 with some associated stack cost of calling out to subroutines. Further,
 each thread stack is used for saving its own registers on a context
 switch, and there is no separate interrupt stack which means that each
 thread stack has to be able to cope with the maximum stack usage of the
 kernel (and application) interrupt handlers.
 Clearly the stack requirement for each thread depends on what your
 application code does, and what memory model is used etc, but generally
 you should find that 128 bytes is enough to allow for the thread to be
 switched out (and thus save its registers) while deep within a kernel
 or application call stack, and similarly enough to provide stack for
 interrupt handlers interrupting while the thread is deep within a kernel
 or application call stack. You will need to increase this depending on
 what level of stack the application code in question requires.
 At this time the maximum stack consumed by the test threads within the
 automated test modules is 95 bytes of stack, and the main test thread has
 been seen to consume 163 bytes of stack. At this time the timer2 test is
 the largest consumer of test thread stack (95 bytes) and the sem3 test
 consumes the largest main thread stack (163 bytes). If your applications
 have large amounts of local data or call several subroutines then you may
 find that you need larger than 128 bytes.
 You may monitor the stack usage of your application threads during runtime
 by defining the macro ATOM_STACK_CHECKING and calling
 atomThreadStackCheck(). This macro is defined by default in the Makefile
 so that the automated test modules can check for stack overflows, but you
 may wish to undefine this in your application Makefiles when you are happy
 that the stack usage is acceptable. Enabling ATOM_STACK_CHECKING will
 increase the size of your threads' TCBs slightly, and will incur a minor
 CPU cycles overhead whenever threads are created due to prefilling the
 thread stack with a known value.
 With careful consideration and few threads it would be possible to use
 a platform with 512 bytes RAM, but not all of the automated test suite
 would run on such a platform (some of the test modules use 6 threads: a
 main thread together with 4 test threads and the idle thread).
 The RAM layout used for the automated test applications is as follows:
 RAM Top:
 * Startup Stack (64 bytes)
 * Data & BSS area (thread stacks, other application data)
 RAM Bottom.
 This is not prescribed, you may use whichever layout you wish for your
 applications.
 The startup stack area starts at the top of RAM and is only used for first
 initialisation of the OS and main thread. This uses 64 bytes and could be
 reused once the OS is started, but for the purposes of the automated test
 applications it is not reused. Generally you would ensure that this is
 reused in your own application code.
 The application's data starts at the bottom of RAM, and this includes all
 of the thread stacks which are statically allocated arrays. The idle
 thread, main thread, and automated test thread stacks are allocated here.
 The default layout provided with Atomthreads matches the STM8S-Discovery
 with 2KB RAM. The linker file reserves the first 0x7C0 bytes for data
 areas. The region from here up to the end of RAM (0x800) is used for the
 the 64 byte startup stack.
 As mentioned previously, this RAM layout is only the one utilised by the
 test applications. You may choose whatever layout you like.
 Note that on this platform data can be placed at address 0x0, but the
 Atomthreads kernel performs validity checks on pointers to ensure they
 are not NULL pointers (point to address 0x0). For this reason the
 example projects (STVD and Makefile) force the linker to not use address
 0x0 and instead start the page0 space at 0x2. This ensures that the
 linker does not place any data at address 0x0, and hence all NULL-ptr
 checks are still suitable checks for valid pointers. This does, however,
 waste 2 bytes. For your own projects you can force this within STVD by
 editing the project linker settings (Input -> Zero Page start at 0x2)
 or by editing the linker .LKF file as can be seen in atomthreads.lkf.
 ---------------------------------------------------------------------------
 INTERRUPT HANDLING
 Interrupt handlers use the stack of the thread which was running when the
 interrupt occurred. If no thread rescheduling occurs during the ISR then
 on exit from the ISR any data stacked by the ISR on the thread's stack is
 popped off the stack and execution of the thread resumes. If a reschedule
 during the ISR causes a context switch to a new thread, then the ISR's
 data will remain on the thread's stack until the thread is scheduled back
 in.
 Interrupt priorities (via the ITC_SPRx registers) are left in their
 default power-on state, which disables interrupt nesting. Kernel changes
 may be required to support interrupt nesting.
 Note that the STM8 programming manual currently describes the following
 feature:
 "Fast interrupt handling through alternate register files (up to 4
  contexts) with standard stack compatible mode (for real time OS
  kernels)"
 This feature was implemented by ST in the core but has to date never been
 included in any STM8 products. If it is included in future products then
 you will need to put the device in the stack compatible mode described.
 ---------------------------------------------------------------------------
 WRITING NEW INTERRUPT HANDLERS
 All interrupt handlers which will call out to the OS kernel and potentially
 cause a thread switch must call atomIntEnter() and atomIntExit(). An
 example of this can be seen in the timer tick ISR in atomport.c.
 With the Cosmic compiler port it is also necessary to add the @svlreg
 modifier to any interrupt handlers which call out to the OS kernel.
 Alternatively you may use the INTERRUPT macro from atomport-private.h which
 always adds the @svlreg modifier. This modifier ensures that the c_lreg
 virtual register is saved on the interrupted thread's stack for any
 preemptive context switches. It also ensures that longs are available for
 use within any OS kernel code called as part of the interrupt handling. 
 You may also implement fast interrupt handlers in the system which do not
 call atomIntEnter()/atomIntExit() and which do not need the @svlreg
 modifier, however these ISRs cannot perform OS functions such as posting
 semaphores or effecting a thread switch.
 ---------------------------------------------------------------------------
 COSMIC COMPILER VIRTUAL REGISTERS
--- a/ports/stm8/README-IAR
+++ b/ports/stm8/README-IAR
@@ -13,43 +13,10 @@ This folder contains a port of the Atomthreads real time kernel for the
 STM8 processor architecture. These instructions cover usage of Atomthreads
 with the IAR Embedded Workbench compiler (EWSTM8).
-All of the cross-platform kernel code is contained in the top-level 
+Compiler-agnostic aspects of the usage of Atomthreads can be found in README.
 'kernel' folder, while ports to specific CPU architectures are contained in
 the 'ports' folder tree. A port to a CPU architecture can comprise just one
 or two modules which provide the architecture-specific functionality, such
 as the context-switch routine which saves and restores processor registers
 on a thread switch. In this case, the kernel port is split into two files:
- * atomport.c: Those functions which can be written in C
+Instructions for users of the other compilers are available in README-SDCC,
- * atomport-asm-iar.s: The main register save/restore assembler routines
+README-COSMIC and README-RAISONANCE.
 Each Atomthreads port requires also a header file which describes various
 architecture-specific details such as appropriate types for 8-bit, 16-bit
 etc variables, the port's system tick frequency, and macros for performing
 interrupt lockouts / critical sections:
 * atomport.h: Port-specific header required by the kernel for each port
 A few additional source files are also included here:
 * tests-main.c: Main application file (used for launching automated tests)
 * uart.c: UART wrapper to allow use of stdio/printf()
 * stm8s-periphs/*.*: Peripheral drivers as delivered by ST (no changes
     to distributed code).
 Atomthreads includes a suite of automated tests which prove the key OS
 functionality, and can be used with any architecture ports. This port
 provides an easy mechanism for building, downloading and running the test
 suite to prove the OS on your target.
 The port was carried out and tested on an STM8S105C6 running within an
 STM8S-Discovery board, and supports the Cosmic, Raisonance and IAR compiler
 tools. It is possible to use it with other processors in the STM8 range, as
 well as other hardware platforms and compilers, with minimal changes.
 Platform and compiler specific code has been kept to an absolute minimum.
 This README covers usage of Atomthreads with the IAR compiler. Instructions
 for users of the other compilers are available in README-COSMIC and
 README-RAISONANCE.
 ---------------------------------------------------------------------------
@@ -188,50 +155,6 @@ device and start it running.
 Other programming tools may exist but are not apparent in the toolset
 delivered for use the STM8S Discovery platform.
 ---------------------------------------------------------------------------
 STM8S-DISCOVERY SPECIFICS
 There are very minimal board-specific aspects to the STM8 port so it is
 trivial to run Atomthreads on other STM8 platforms.
 The test applications make use of a LED to indicate test pass/fail status.
 This is currently configured to use a bit in GPIOD, which on the Discovery
 board maps to the board's only LED. You may change the port and register
 bit in tests-main.c to utilise a different pin on other hardware platforms.
 You may also completely omit the LED flashing in the test application if
 you prefer to use the UART for monitoring test status.
 The test applications also make use of the UART to print out pass/fail
 indications and other information. For this you should connect a serial
 cable to the Discovery board via the external pin connectors. Use of
 a UART is not required if you prefer to use the LED or some other method
 of notifying test pass/fail status.
 To connect a serial cable to the Discovery you will need to connect to
 the following pins on the external connectors:
 Vcc: CN2 pin 8
 GND: CN2 pin 7
 UART RX: CN4 pin 11 (connect to TX at the PC end)
 UART TX: CN4 pin 10 (connect to RX at the PC end)
 Note that the board uses TTL levels so you may need to use a level
 converter. External level converters may need to be powered using
 a Vdd of 5v, which can be achieved by positioning JP1 on the Discovery.
 The STM8 device on the Discovery only offers UART2. If you are using a
 different device or wish to use an alternative UART then you must change
 the stm8s_conf.h file.
 If you are using a CPU other than the STM8S105C6 you should change the
 PART macro from "STM8S105" to your target CPU. This can be changed in the
 iar.mak Makefile. If you are using the EWSTM8 project it should be
 changed in the project C/C++ Compiler Preprocessor settings for both Debug
 and Release builds, and you must also change the target device in the
 project's "General Options". You may also wish to enable any CPU
 peripherals which you wish to use in the stm8s_conf.h file.
 ---------------------------------------------------------------------------
 RUNNING THE AUTOMATED TESTS
@@ -311,107 +234,6 @@ Add the .C and .S modules from the following folders:
 Set include paths as appropriate.
 ---------------------------------------------------------------------------
 RAM FOOTPRINT & STACK USAGE
 The Atomthreads kernel is written in well-structured pure C which is highly
 portable and not targeted at any particular compiler or CPU architecture.
 For this reason it is not highly optimised for the STM8 architecture, and
 by its nature will likely have a higher text and data footprint than an
 RTOS targeted at the STM8 architecture only. The emphasis here is on
 C-based portable, readable and maintainable code which can run on any CPU
 architecture, from the 8-bitters up.
 A good rule of thumb when using Atomthreads on the STM8 architecture is
 that a minimum of 1KB RAM is required in order to support an application
 with 4 or 5 threads and the idle thread. If a minimum of approximately
 128 bytes per thread stack is acceptable then you will benefit from the
 easy-to-read, portable implementation of an RTOS herein.
 The major consumer of RAM when using Atomthreads is your thread stacks.
 Functionality that is shared between several kernel modules is farmed out
 to separate functions, resulting in readable and maintainable code but
 with some associated stack cost of calling out to subroutines. Further,
 each thread stack is used for saving its own registers on a context
 switch, and there is no separate interrupt stack which means that each
 thread stack has to be able to cope with the maximum stack usage of the
 kernel (and application) interrupt handlers.
 Clearly the stack requirement for each thread depends on what your
 application code does, and what memory model is used etc, but generally
 you should find that 128 bytes is enough to allow for the thread to be
 switched out (and thus save its registers) while deep within a kernel
 or application call stack, and similarly enough to provide stack for
 interrupt handlers interrupting while the thread is deep within a kernel
 or application call stack. You will need to increase this depending on
 what level of stack the application code in question requires.
 At this time the maximum stack consumed by the test threads within the
 automated test modules is 85 bytes of stack, and the main test thread has
 been seen to consume 193 bytes of stack. At this time the queue9 test is
 the largest consumer of test thread stack (85 bytes) and the sem8 test
 consumes the largest main thread stack (193 bytes). If your applications
 have large amounts of local data or call several subroutines then you may
 find that you need larger than 128 bytes.
 You may monitor the stack usage of your application threads during runtime
 by defining the macro ATOM_STACK_CHECKING and calling
 atomThreadStackCheck(). This macro is defined by default in the EWSTM8
 Debug project so that the automated test modules can check for stack
 overflows, but you may wish to undefine this in your application
 when you are happy that the stack usage is acceptable. Enabling 
 ATOM_STACK_CHECKING will increase the size of your threads' TCBs
 slightly, and will incur a minor CPU cycles overhead whenever threads are
 created due to prefilling the thread stack with a known value.
 With careful consideration and few threads it would be possible to use
 a platform with 512 bytes RAM, but not all of the automated test suite
 would run on such a platform (some of the test modules use 6 threads: a
 main thread together with 4 test threads and the idle thread).
 ---------------------------------------------------------------------------
 INTERRUPT HANDLING
 Interrupt handlers use the stack of the thread which was running when the
 interrupt occurred. If no thread rescheduling occurs during the ISR then
 on exit from the ISR any data stacked by the ISR on the thread's stack is
 popped off the stack and execution of the thread resumes. If a reschedule
 during the ISR causes a context switch to a new thread, then the ISR's
 data will remain on the thread's stack until the thread is scheduled back
 in.
 Interrupt priorities (via the ITC_SPRx registers) are left in their
 default power-on state, which disables interrupt nesting. Kernel changes
 may be required to support interrupt nesting.
 Note that the STM8 programming manual currently describes the following
 feature:
 "Fast interrupt handling through alternate register files (up to 4
  contexts) with standard stack compatible mode (for real time OS
  kernels)"
 This feature was implemented by ST in the core but has to date never been
 included in any STM8 products. If it is included in future products then
 you will need to put the device in the stack compatible mode described.
 ---------------------------------------------------------------------------
 WRITING NEW INTERRUPT HANDLERS
 All interrupt handlers which will call out to the OS kernel and potentially
 cause a thread switch must call atomIntEnter() and atomIntExit(). An
 example of this can be seen in the timer tick ISR in atomport.c.
 You may also implement fast interrupt handlers in the system which do not
 call atomIntEnter()/atomIntExit(), however these ISRs cannot perform OS
 functions such as posting semaphores or effecting a thread switch.
 ---------------------------------------------------------------------------
 IAR COMPILER VIRTUAL REGISTERS
--- a/ports/stm8/README-RAISONANCE
+++ b/ports/stm8/README-RAISONANCE
@@ -13,43 +13,10 @@ This folder contains a port of the Atomthreads real time kernel for the
 STM8 processor architecture. These instructions cover usage of Atomthreads
 with the Raisonance compiler (RCSTM8).
-All of the cross-platform kernel code is contained in the top-level 
+Compiler-agnostic aspects of the usage of Atomthreads can be found in README.
 'kernel' folder, while ports to specific CPU architectures are contained in
 the 'ports' folder tree. A port to a CPU architecture can comprise just one
 or two modules which provide the architecture-specific functionality, such
 as the context-switch routine which saves and restores processor registers
 on a thread switch. In this case, the kernel port is split into two files:
- * atomport.c: Those functions which can be written in C
+Instructions for users of the other compilers are available in README-SDCC,
- * atomport-asm-raisonance.s: Main register save/restore assembler routines
+README-IAR and README-COSMIC.
 Each Atomthreads port requires also a header file which describes various
 architecture-specific details such as appropriate types for 8-bit, 16-bit
 etc variables, the port's system tick frequency, and macros for performing
 interrupt lockouts / critical sections:
 * atomport.h: Port-specific header required by the kernel for each port
 A few additional source files are also included here:
 * tests-main.c: Main application file (used for launching automated tests)
 * uart.c: UART wrapper to allow use of stdio/printf()
 * stm8s-periphs/*.*: Peripheral drivers as delivered by ST (no changes
     to distributed code).
 Atomthreads includes a suite of automated tests which prove the key OS
 functionality, and can be used with any architecture ports. This port
 provides an easy mechanism for building, downloading and running the test
 suite to prove the OS on your target.
 The port was carried out and tested on an STM8S105C6 running within an
 STM8S-Discovery board, and supports the Cosmic, Raisonance and IAR compiler
 tools. It is possible to use it with other processors in the STM8 range, as
 well as other hardware platforms and compilers, with minimal changes.
 Platform and compiler specific code has been kept to an absolute minimum.
 This README covers usage of Atomthreads with the Raisonance compiler.
 Instructions for users of the other compilers are available in README-IAR
 and README-COSMIC.
 ---------------------------------------------------------------------------
@@ -204,49 +171,6 @@ device and start it running.
 Other programming tools may exist but are not apparent in the toolset
 delivered for use the STM8S Discovery platform.
 ---------------------------------------------------------------------------
 STM8S-DISCOVERY SPECIFICS
 There are very minimal board-specific aspects to the STM8 port so it is
 trivial to run Atomthreads on other STM8 platforms.
 The test applications make use of a LED to indicate test pass/fail status.
 This is currently configured to use a bit in GPIOD, which on the Discovery
 board maps to the board's only LED. You may change the port and register
 bit in tests-main.c to utilise a different pin on other hardware platforms.
 You may also completely omit the LED flashing in the test application if
 you prefer to use the UART for monitoring test status.
 The test applications also make use of the UART to print out pass/fail
 indications and other information. For this you should connect a serial
 cable to the Discovery board via the external pin connectors. Use of
 a UART is not required if you prefer to use the LED or some other method
 of notifying test pass/fail status.
 To connect a serial cable to the Discovery you will need to connect to
 the following pins on the external connectors:
 Vcc: CN2 pin 8
 GND: CN2 pin 7
 UART RX: CN4 pin 11 (connect to TX at the PC end)
 UART TX: CN4 pin 10 (connect to RX at the PC end)
 Note that the board uses TTL levels so you may need to use a level
 converter. External level converters may need to be powered using
 a Vdd of 5v, which can be achieved by positioning JP1 on the Discovery.
 The STM8 device on the Discovery only offers UART2. If you are using a
 different device or wish to use an alternative UART then you must change
 the stm8s_conf.h file.
 If you are using a CPU other than the STM8S105C6 you should change the
 PART macro from "STM8S105" to your target CPU. This can be changed in the
 raisonance.mak Makefile. If you are using the STVD project it should be
 changed in the project preprocessor settings for both Debug and Release
 builds. You may also wish to enable any CPU peripherals which you wish to
 use in the stm8s_conf.h file.
 ---------------------------------------------------------------------------
 RUNNING THE AUTOMATED TESTS
@@ -318,106 +242,6 @@ functions in reentrant mode, however it does this by default on the STM8
 platform so no user action is required (unlike when targeting the STM7
 platform with Raisonance).
 ---------------------------------------------------------------------------
 RAM FOOTPRINT & STACK USAGE
 The Atomthreads kernel is written in well-structured pure C which is highly
 portable and not targeted at any particular compiler or CPU architecture.
 For this reason it is not highly optimised for the STM8 architecture, and
 by its nature will likely have a higher text and data footprint than an
 RTOS targeted at the STM8 architecture only. The emphasis here is on
 C-based portable, readable and maintainable code which can run on any CPU
 architecture, from the 8-bitters up.
 A good rule of thumb when using Atomthreads on the STM8 architecture is
 that a minimum of 1KB RAM is required in order to support an application
 with 4 or 5 threads and the idle thread. If a minimum of approximately
 128 bytes per thread stack is acceptable then you will benefit from the
 easy-to-read, portable implementation of an RTOS herein.
 The major consumer of RAM when using Atomthreads is your thread stacks.
 Functionality that is shared between several kernel modules is farmed out
 to separate functions, resulting in readable and maintainable code but
 with some associated stack cost of calling out to subroutines. Further,
 each thread stack is used for saving its own registers on a context
 switch, and there is no separate interrupt stack which means that each
 thread stack has to be able to cope with the maximum stack usage of the
 kernel (and application) interrupt handlers.
 Clearly the stack requirement for each thread depends on what your
 application code does, and what memory model is used etc, but generally
 you should find that 128 bytes is enough to allow for the thread to be
 switched out (and thus save its registers) while deep within a kernel
 or application call stack, and similarly enough to provide stack for
 interrupt handlers interrupting while the thread is deep within a kernel
 or application call stack. You will need to increase this depending on
 what level of stack the application code in question requires.
 At this time the maximum stack consumed by the test threads within the
 automated test modules is 95 bytes of stack, and the main test thread has
 been seen to consume 163 bytes of stack. At this time the queue9 test is
 the largest consumer of test thread stack (95 bytes) and the sem1 test
 consumes the largest main thread stack (137 bytes). If your applications
 have large amounts of local data or call several subroutines then you may
 find that you need larger than 128 bytes.
 You may monitor the stack usage of your application threads during runtime
 by defining the macro ATOM_STACK_CHECKING and calling
 atomThreadStackCheck(). This macro is defined by default in the Makefile
 so that the automated test modules can check for stack overflows, but you
 may wish to undefine this in your application Makefiles when you are happy
 that the stack usage is acceptable. Enabling ATOM_STACK_CHECKING will
 increase the size of your threads' TCBs slightly, and will incur a minor
 CPU cycles overhead whenever threads are created due to prefilling the
 thread stack with a known value.
 With careful consideration and few threads it would be possible to use
 a platform with 512 bytes RAM, but not all of the automated test suite
 would run on such a platform (some of the test modules use 6 threads: a
 main thread together with 4 test threads and the idle thread).
 ---------------------------------------------------------------------------
 INTERRUPT HANDLING
 Interrupt handlers use the stack of the thread which was running when the
 interrupt occurred. If no thread rescheduling occurs during the ISR then
 on exit from the ISR any data stacked by the ISR on the thread's stack is
 popped off the stack and execution of the thread resumes. If a reschedule
 during the ISR causes a context switch to a new thread, then the ISR's
 data will remain on the thread's stack until the thread is scheduled back
 in.
 Interrupt priorities (via the ITC_SPRx registers) are left in their
 default power-on state, which disables interrupt nesting. Kernel changes
 may be required to support interrupt nesting.
 Note that the STM8 programming manual currently describes the following
 feature:
 "Fast interrupt handling through alternate register files (up to 4
  contexts) with standard stack compatible mode (for real time OS
  kernels)"
 This feature was implemented by ST in the core but has to date never been
 included in any STM8 products. If it is included in future products then
 you will need to put the device in the stack compatible mode described.
 ---------------------------------------------------------------------------
 WRITING NEW INTERRUPT HANDLERS
 All interrupt handlers which will call out to the OS kernel and potentially
 cause a thread switch must call atomIntEnter() and atomIntExit(). An
 example of this can be seen in the timer tick ISR in atomport.c.
 You may also implement fast interrupt handlers in the system which do not
 call atomIntEnter()/atomIntExit(), however these ISRs cannot perform OS
 functions such as posting semaphores or effecting a thread switch.
 ---------------------------------------------------------------------------
--- a/ports/stm8/README-SDCC
+++ b/ports/stm8/README-SDCC
@@ -1,18 +1,61 @@
 ---------------------------------------------------------------------------
 Author: Dr. Philipp Klaus Krause
 ---------------------------------------------------------------------------
 STM8 PORT - SMALL DEVICE C COMPILER
 This folder contains a port of the Atomthreads real time kernel for the
 STM8 processor architecture. These instructions cover usage of Atomthreads
 with the Small Device C Compiler (SDCC).
 This README covers usage of Atomthreads with SDCC.
 Instructions for users of the other compilers are available in README-COSMIC,
 README-IAR and README-RAISONANCE.
 ---------------------------------------------------------------------------
 PREREQUISITES
- * SDCC
+The port works out-of-the-box with SDCC and GNU make for
 building.
 * SDCC 3.6.0 or later
 * Programming software (e.g. stm8flash)
 ---------------------------------------------------------------------------
 BUILD VIA MAKEFILE
 * make -f sdcc.mak
 All objects are built into the 'build-sdcc' folder under ports/stm8.
 The build process builds separate target applications for each automated
 test, and appropriate .ihx files can be found in the build folder
 ready for downloading to and running on the target. Because of the limited
 resources on the STM8, and the large amount of automated tests, each test
 is built and run as a separate application.
 All built objects etc can be cleaned using:
 * make -f sdcc.mak clean
 The Atomthreads sources are documented using Doxygen markup. You can build
 both the kernel and STM8 port documentation from this folder using:
 * make -f raisonance.mak doxygen
 ---------------------------------------------------------------------------
 PROGRAMMING MAKEFILE-BUILT APPLICATIONS TO THE TARGET DEVICE
 Applications can be written onto the STM8S-Discovery board using:
 * stm8flash -c stlink -p stm8s105c6 -w <filename>
 ---------------------------------------------------------------------------