ensures that the assembler generates instructions for the C167 (as opposed to XC167) Memory models The system startup file

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System Startup Detailed -1 week lecture Topics 4 System Startup Detailed - ( TASKING) Macro definitions, configuration registers and stack frames - and memory maps - Memory type specifiers - Object

asm example System Startup Detailed -2 - Compiler dependent; TASKING C166 tool chain uses a generic assembler file called start.asm - Macros are used to configure this file, e.g. $MOD167 $CASE etc.

1 System Startup Detailed -1 week lecture Topics 4 System Startup Detailed - ( TASKING) Macro definitions, configuration registers and stack frames - and memory maps - Memory type specifiers - Object classes and storage class - Segmented / non-segmented addressing - start.asm example System Startup Detailed -2 - Compiler dependent; TASKING C166 tool chain uses a generic assembler file called start.asm - Macros are used to configure this file, e.g. $MOD167 $CASE etc. ensures that the assembler generates instructions for the C167 (as opposed to XC167) enable case sensitive preprocessing of this file System Startup Detailed -3 C166/ST10 startup code generated by EDE for project toggle_led If modifications are needed, disable generation of the startup code in EDE: In the EDE Project Options dialog select Application, and then Startup. Make sure the checkbox 'Generate system startup code and add it to project' is not checked. Note that changes in EDE will now no longer be reflected in the startup code. Also be aware that the modifications will be overwritten when the checkbox is enabled again. $EXTEND2 $CASE $GENONLY $DEBUG $NOLOCALS $CHECKCPU16 $NOMOD166 $STDNAMES(regxc167ci.def) ; disable the internal set of SFRs ; define SFRs System Startup Detailed -4 are compiler specific features and are therefore described in the compiler manuals ( )

System Startup Detailed -5 - define default mappings for variable declarations without memory type specifier - The memory type specifier of an object (variable or function) tells the compiler to

2 System Startup Detailed -5 - define default mappings for variable declarations without memory type specifier - The memory type specifier of an object (variable or function) tells the compiler to which object class it is to be assigned - The object class is used by the linker to locate an object to an absolute address - This correspondence is defined in a memory map; the programmer thus has complete control over where in memory an object will end up, e.g. internal / external RAM or ROM, EEPROM, etc. System Startup Detailed -6 object classes - Object classes are either CODE, CONST or DATA - The objects within any of these classes can be accessed using Near, Far, Huge or Xhuge addresses (hence, NDATA are variables which are addressed using paged bit addresses, etc.) - A class name ending on 0 indicates that the associated memory is to be erased at system start - Names beginning with I refer to classes within the on-chip RAM or ROM; names beginning with B refer to bit-addressable memory; S stands for the system page (0xC000 to 0xFFFF, page 3) System Startup Detailed -7 memory types Object classes are assigned based on the memory type of a variable System Startup Detailed -8 memory type - Near addresses contain two bytes (16-bit) - A near address is interpreted as linear 16-bit address when the CPU is running in non-segmented mode; non-segmented mode restricts the address space to the first 64 kbyte (default) - In segmented mode, a near address consists of a Data-Page Pointer selector and a linear offset: DPP selector linear 14-bit offset

3 System Startup Detailed -9 memory type - Far addresses contain two words (32-bit) - A far address consists of a linear 14-bit offset (this limits the maximum object size to 16 kbyte) and for function pointers: a segment number (0 255) for variable addresses: a page number (0 1023) - Far functions: address = (segm * 0x10000) + offset Far variables: address = (page * 0x4000) + offset X X X X X X 0 0 unused page/segment linear 14-bit offset System Startup Detailed -10 memory type - Huge/Xhuge addresses contain two words (32-bit) - A huge (data) address consists of a linear 16-bit offset (limits the maximum object size to 64 kbyte) and a segment number (0 255) - Huge address = (segment * 0x10000) + offset X X X X X X X X unused segment linear 16-bit offset - An Xhuge (data) address is simply a linear 32-bit address (unlimited object size, i. e. 16 MB) System Startup Detailed -11 memory type - Huge/Xhuge pointers are only useful with variables - For function calls, huge, xhuge and far pointers are identical: they consist of an 8-bit segment number and a 16-bit linear address offset - Example: char xhuge myvariable[0x20000]; This defines an xhuge character array with a total size of 128 kbyte; note that access to the elements above 64k is not possible with a far address! (This would require a new segment number to be loaded) System Startup Detailed The TASKING C166 compiler provides 5 memory models: TINY, SMALL, MEDIUM, LARGE and HUGE - These memory models define the default memory type to be used for function calls and variables - These defaults can usually be overridden by an explicit declaration, e.g. char far myarray[1024]; void far mysubroutine(void);

System Startup Detailed -13 System Startup Detailed -14 - The memory models of the TASKING C166 - All models but TINY run in segmented CPU mode - TINY: non-segmented CPU mode; all code/data access

4 System Startup Detailed -13 System Startup Detailed The memory models of the TASKING C166 - All models but TINY run in segmented CPU mode - TINY: non-segmented CPU mode; all code/data access via linear 16-bit addresses address space: 64kB specifiers far, huge and xhuge are not permitted - Note that not all compilers define memory models (Metrowerks CodeWarrior uses #pragma directives) System Startup Detailed -15 System Startup Detailed SMALL - SMALL: segmented CPU mode; variables are in the near area and function calls generate near addresses; code and data can be located outside the first 64k; overriding specifiers far, huge and xhuge are permitted - is the most used memory model - allows a total code size up to 16M, - up to 64K of fast accessible 'normal user data' - the possibility to access far/huge data, if more than 64K of data is needed. default (start-up value): DPP0:0 DPP1:1 DPP3:3 DPP2:2 Address linear: DPP0:n DPP1:n+1 DPP3:3 DPP2:n+2 SND: DPP0:x DPP1:y DPP3:3 DPP2:z

5 System Startup Detailed -17 System Startup Detailed SMALL - MEDIUM: - default code size: 64kB (segment 0) - code in other segments allowed but with limitation - used for large data access: far data - small portion of a fast-access data: xnear - huge, shuge data allowed System Startup Detailed -19 System Startup Detailed preprocessor symbol _MODEL - LARGE: access to data as well as functions calls generate far addresses; used with large programs having large data size requirements - native: far data (16MB, max. size 16kB) - HUGE: access to data as well as functions calls generate huge addresses; native: huge data total: 16MB, struct size < 64kB, arrays >64kB

System Startup Detailed -21 TASKING IDE System Startup Detailed -22 memory map - The memory map assigns each object class to an absolute address range; together with the specifics of the underlying

etc.) or scope modifiers (const, volatile, etc.) provides further mechanisms to locate objects in memory.

6 System Startup Detailed -21 TASKING IDE System Startup Detailed -22 memory map - The memory map assigns each object class to an absolute address range; together with the specifics of the underlying hardware (type and configuration of the controller, external memory and peripherals) this defines where stuff goes - Note that the explicit use of storage class specifiers (static, automatic, extern, etc.) or scope modifiers (const, volatile, etc.) provides further mechanisms to locate objects in memory. For example, an object which has been declared as const is located in N/F/HCONST (which is usually mapped to ROM) System Startup Detailed -23 memory map System Startup Detailed -24 memory map - The memory map is specified to the linker (e.g. on the command line, in the menus of the IDE, in form of a linker map file, etc.) - Example for the KEIL linker (L166): L166 myprog.obj \ CLASSES (FCODE(0x x00BFFF, 0x x03FFFF), \ NCONST(0x00C000-0x00DFFF), FCONST(0x00C000-0x00DFFF), \ NDATA(0x x10BFFF), NDATA0(0x x10BFFF), FDATA(0x10C000-0x13FFFF), FDATA0(0x10C000-0x13FFFF) ) - Far data can be found from 0x10C000 onwards, the code is at 0 0xBFFF and 0x x3FFFF, constants (near and far) are located above 0xC000

System Startup Detailed -25 memory map System Startup Detailed -26 - BUSCON registers configure the External Bus Controller (EBC); the external bus can be enabled or disabled, it can be configured to

7 System Startup Detailed -25 memory map System Startup Detailed BUSCON registers configure the External Bus Controller (EBC); the external bus can be enabled or disabled, it can be configured to be an 8-bit multiplexed bus, a 16-bit non-multiplexed bus,, read/write access to the bus can be slowed down using wait states, etc. - SYSCON registers configure the controller itself; control of the internal XBUS, the watchdog oscillator, the internal ROM, the CPU (e.g. segmented mode or not), the system stack size, the behaviour following a hardware reset, etc. System Startup Detailed -27 System Startup Detailed -28 C166/ST10 startup code generated by EDE for project pmu If modifications are needed, disable generation of the startup code in EDE: In the EDE Project Options dialog select Application, and then Startup. Make sure the checkbox 'Generate system startup code and add it to project' is not checked. Note that changes in EDE will now no longer be reflected in the startup code. Also be aware that the modifications will be overwritten when the checkbox is enabled again. $EXTEND2 $CASE $GENONLY $DEBUG $NOLOCALS $CHECKCPU16 $CHECKBUS18 $NOMOD166 $STDNAMES(regxc161cj.def) $INCLUDE(head.asm) $INCLUDE(_c_init.asm) ; disable the internal set of SFRs ; define SFRs ; Generic definitions (see product include dir) ; Initialize C variables

System Startup Detailed -29 NAME CSTART ; module name System Startup Detailed -30 Project specific PUBLIC IDLE ; cstart end PUBLIC EXIT ; address to jump to on 'exit()' EXTERN _main:far ; start label

R0,#0x6243 MOV SYSCON3, #0x7310 MOV R0,#0x4055 MOV EBCMOD0, R0 Project specific System Startup Detailed -31 ATOMIC #4 MOV SPSEG, #0x0000 ; Set stack segment MOV SP, #SOF?

8 System Startup Detailed -29 NAME CSTART ; module name System Startup Detailed -30 Project specific PUBLIC IDLE ; cstart end PUBLIC EXIT ; address to jump to on 'exit()' EXTERN _main:far ; start label user program EXTERN C_INIT:FAR EXTERN _sim_reseteinit:far CSTART_PR SECTION CODE WORD PUBLIC 'CPROGRAM' CSTART PROC TASK CSTART_TASK INTNO CSTART_INUM = 0 MOV CPUCON1, #0x0007 MOV SPSEG, #0x0000 MOV R0,#0x6243 MOV SYSCON3, #0x7310 MOV R0,#0x4055 MOV EBCMOD0, R0 Project specific System Startup Detailed -31 ATOMIC #4 MOV SPSEG, #0x0000 ; Set stack segment MOV SP, #SOF?SYSSTACK_TOP ; Set stack pointer. MOV STKOV, #SOF?SYSSTACK_BOTTOM + 6*2; Set stack overflow pointer. MOV STKUN, #SOF?SYSSTACK_TOP ; Set stack underflow pointer. MOV CP, #CSTART_RBANK ; Set context pointer. NOP MOV DPP0, #PAG?BASE_DPP0 ; Set data page pointer. MOV DPP1, #PAG?BASE_DPP1 ; Initialise these before we can make a MOV DPP2, #PAG?BASE_DPP2 ; user stack call below MOV R0, #?USRSTACK_TOP ; set user stack pointer BFLDH PSW, #3, #2 ; set local register bank 0 (10) MOV R0, #?USRSTACK0_TOP ; set user stack pointer BFLDH PSW, #3, #3 ; set local register bank 1 (11) System Startup Detailed -32 ATOMIC #4 BFLDH PSW, #3, #0 ; set to global user _sim_reseteinit, R1) ; Set and service watchdog timer after CALLEINIT, so cause of reset ; can be determined there. DISWDT BIT_INIT, 0 C_INIT, R1) MOV R12, #0 ; set argc to 0 MOV R13, #0 ; MOV R14, #0 ; set argv[] to 0 ; Disable watchdog timer ; End of initialization ; disable(0)/enable(1) initialization of bit ; variables at startup ; initalization of global/static data MOV R0, #?USRSTACK1_TOP ; set user stack _main, R1)

9 System Startup Detailed Other compilers use different but similar startup files: Metrowerks CodeWarrior uses a C-language file called start12.c, GNU gcc uses a very compact assembler language file called crt0.s - Compiled versions of these modules can often be found in the system libraries; in this case, they do not have to be included in the build process provided the application is linked against these libraries (e.g. libgcc.a for GNU gcc, etc.) System Startup Detailed Fundamental tasks common to all startup modules: Reset Initialisation of the stack pointer (SP) Clearing of the block storage segment (bss), if required Copy initialized variables from ROM to RAM, if req. Call main Always required, one of the first things to be done Not required if all variables are initialised at run-time Not required if all variables are initialised at run-time

C167 (as opposed to C166, C164) - Compiler dependent; KEIL C166 tool chain uses a. generates instructions for the

C167 (as opposed to C166, C164) - Compiler dependent; KEIL C166 tool chain uses a. generates instructions for the System Startup Detailed MP4-1 System Startup Detailed MP4-2 week lecture Topics 4 System Startup Detailed - (example: KEIL) Macro definitions, configuration registers and stack frames - and memory maps