1. UEE072HM

2. Embedded and Real-Time Systems We will mainly look at embedded systems –Systems which have the computer system embedded within their application area, normally using a specialised single board computer (SBC) –There is a difference between embedded and real-time – one does not imply the other –Hard real-time vs soft real-time

3. Embedded Systems Development Embedded systems require host-target development – this means –The development is done on a different machine than the target –The code must be downloaded to run –Can be running on different CPU and architecture

5. Embedded Systems Development Embedded systems development requires –Mixed language programming – HLL plus assembler –Increased knowledge of tools – compiler, linker and librarians –Use of specialised tools – i.e. down loaders –Special skills to debug code

6. Using C for Embedded Systems A major requirement is for direct memory access, this is achieved using pointers. This style of code is quite common #define ADDRESS 0xFFFF41 main() { char *mem_p; mem_p=(char*)ADDRESS; while !(*mem_p ) ;// do nothing }

7. Using C for Embedded Systems Note –Use of # define –Use of char * –Use of volatile –Casting of return value –Use of binary op & #define ADDRESS 0xFFFF41 #define MASK 0x3 main() { volatile char *mem_p; mem_p=(char*)ADDRESS; while !(*mem_p & MASK ) ;// do nothing }

8. Using C for Embedded Systems Using C in Embedded Systems you will need to know more about –Compilation process –Linking –Storage issues

9. Using C for Embedded Systems Compilation issues –Passing parameters –Naming conventions –Symbol table and map generation –Assembler output

10. Using C for Embedded Systems Why link HLL and ALP? –Speed –Special instructions –Code size

11. Using C for Embedded Systems Ways to link HLL & ALP - passing parameters –Parameter blocks No recursion –Using registers Limited numbers of registers –Using the stack Most favoured method –Many use a combination of the above

12. Using C for Embedded Systems Using the stack for parameter passing, it requires –Creation of stack frame/frame pointer –Instructions to allocate/deallocate a stack frame In 68000 –link and unlk instructions

13. Using C for Embedded Systems We need to understand –Program counter –Frame pointer –Stack pointer –Stack

14. Using C for Embedded Systems On reaching the following C instruction –gets(sr) We will get the following 68000 code –jsr _gets()

15. Using C for Embedded Systems Once in gets with the following C –char * gets( chat * s) –{ –int str[10]; The following assembler will be created –_get: –link a5, #-40

16. Using C for Embedded Systems With the following recursive call –char * gets( chat * s) –{ –int str[10]; –gets(sr);

17. Using C for Embedded Systems On the final } or return statement we would get the following 68000 –unlk a5