496 lines
13 KiB
NASM
496 lines
13 KiB
NASM
; ROM.ASM - Aztec Embedded Systems Startup Code
|
|
; Copyright (C) 1984-1992 by Manx Software Systems
|
|
; :ts=8
|
|
; Equates:
|
|
ifndef NEAR_DATA_INIT
|
|
NEAR_DATA_INIT equ 1 ; Set to 0 to disable initialization of _DATA
|
|
endif
|
|
|
|
ifndef FAR_DATA_INIT
|
|
FAR_DATA_INIT equ 0 ; Set to 1 to enable initialization of FAR_DATA
|
|
endif
|
|
|
|
ifndef FAR_BSS_INIT
|
|
FAR_BSS_INIT equ 0 ; Set to 1 to enable initialization of FAR_BSS
|
|
endif
|
|
|
|
ifndef CPU_186
|
|
CPU_186 equ 0 ; Set to 1 if CPU is 80186
|
|
endif
|
|
|
|
;
|
|
include lmacros.h
|
|
;
|
|
; STACK PLACEMENT
|
|
; ---------------
|
|
; If you want your stack at a fixed place, you may remove the
|
|
; "bss cstack..." statement below and change the "mov sp,cstack..."
|
|
; to load SP with the value you desire. Note that the setup of
|
|
; SS may need to be changed also. If the program is small data
|
|
; model, then SS must be equal to DS or pointers to automatic
|
|
; variables on the stack won't work properly. In large data model,
|
|
; there are no restrictions on stack placement.
|
|
;
|
|
; Otherwise, stacksize should be set according to your program's
|
|
; requirements.
|
|
;
|
|
|
|
stacksize equ 80h ; # paras in stack area
|
|
heapsize equ 80h ; # paras in heap area
|
|
|
|
;
|
|
; 80186 CHIP SELECT DEFINITIONS
|
|
; -----------------------------
|
|
; You should define the macro CPU_186 if you're using a 186 processor
|
|
;
|
|
if CPU_186
|
|
|
|
; chip select registers
|
|
UMCS equ 0FFA0h ;Upper memory chip select
|
|
LMCS equ 0FFA2h ;Lower memory chip select
|
|
PACS equ 0FFA4h ;Peripheral chip select
|
|
MPCS equ 0FFA8h ;Middle-memory chip select
|
|
|
|
;
|
|
; Valid values for UMCS
|
|
; The equate for ROM_SZ (below) should be changed to reflect your system's
|
|
; available high-memory ROM size.
|
|
;
|
|
UMBS_1 equ 0FFF8h ;1K
|
|
UMBS_2 equ 0FFB8h ;2K
|
|
UMBS_4 equ 0FF38h ;4K
|
|
UMBS_8 equ 0FE38h ;8K
|
|
UMBS_16 equ 0FC38h ;16K
|
|
UMBS_32 equ 0F838h ;32K
|
|
UMBS_64 equ 0F038h ;64K
|
|
UMBS_128 equ 0E038h ;128K
|
|
UMBS_256 equ 0C038h ;256K
|
|
|
|
;
|
|
; Valid values for LMCS
|
|
; The equate for RAM_SZ (below) should be changed to reflect your
|
|
; system's available low-memory RAM size.
|
|
;
|
|
|
|
LMBS_1 equ 0038h ;1K
|
|
LMBS_2 equ 0078h ;2K
|
|
LMBS_4 equ 00f8h ;4K
|
|
LMBS_8 equ 01f8h ;8K
|
|
LMBS_16 equ 03f8h ;16K
|
|
LMBS_32 equ 07f8h ;32K
|
|
LMBS_64 equ 0ff8h ;64K
|
|
LMBS_128 equ 1ff8h ;128K
|
|
LMBS_256 equ 3ff8h ;256K
|
|
|
|
endif
|
|
|
|
dataseg segment word public 'data'
|
|
|
|
; bss cstack:byte,stacksize shl 4
|
|
global cstack:byte,stacksize shl 4
|
|
;
|
|
; RUN-TIME LIBRARY VARIABLES
|
|
; --------------------------
|
|
; Variables required by the run-time libraries for heap management, error
|
|
; reporting, etc.
|
|
;
|
|
global errno_:word,2
|
|
global _dsval_:word,2
|
|
global _csval_:word,2
|
|
global _mbot_:word,2
|
|
global _mcur_:word,2
|
|
global _mtop_:word,2
|
|
global _sbot_:word,2
|
|
;
|
|
; The variable is used with csav and cret only. Therefore if you do not
|
|
; compile the the +c option or +b option you do not need this.
|
|
;
|
|
public _lowwater_
|
|
_lowwater_ dw -1
|
|
;
|
|
; These variables are used to 'bracket' the code, data, and unitialized
|
|
; data segments. They are initialized by the locator.
|
|
;
|
|
extrn _Dorg_:byte,_Dend_:byte
|
|
extrn _Uorg_:byte,_Uend_:byte
|
|
dataseg ends
|
|
extrn _Corg_:byte,_Cend_:byte
|
|
|
|
ifdef FARPROC
|
|
extrn main_:far, $fltinit:far
|
|
else
|
|
extrn main_:near, $fltinit:near
|
|
endif
|
|
|
|
;------------------------------------------
|
|
; $BEGIN - C initialization routine ;
|
|
;------------------------------------------
|
|
|
|
public $begin
|
|
$begin proc far
|
|
|
|
cli
|
|
cld
|
|
|
|
if CPU_186
|
|
|
|
;
|
|
; 80186 LOW-MEMORY CHIP SELECT INITIALIZATION
|
|
; -------------------------------------------
|
|
; This code intializes the LMCS register, and assumes an 8K
|
|
; RAM size at lower memory. If your RAM size is different, change
|
|
; the RAM_SZ equate below to the appropriate LMBS_X defintion.
|
|
;
|
|
|
|
RAM_SZ equ LMBS_8 ; This assumes a 8K RAM area
|
|
|
|
mov dx,LMCS
|
|
mov ax,RAM_SIZE
|
|
out dx,ax
|
|
|
|
;
|
|
; Additional 80186 chip select and peripheral chip select operations
|
|
; should be done here.
|
|
;
|
|
|
|
endif
|
|
|
|
;
|
|
; COMPUTE WHERE INITIALZED DATA STARTS
|
|
; ------------------------------------
|
|
; This code sets up the following registers:
|
|
; DS - Paragraph address of the end of the 'CODE' class.
|
|
; ES - Paragraph address of the start of the _DATA.
|
|
;
|
|
; Aloc guarantees that class bracket symbols are normalized
|
|
; (i.e., _Cend_'s offset will never be greater than 0x0f), so we have
|
|
; nice tiny code.
|
|
|
|
mov ax,seg _Cend_
|
|
mov ds,ax
|
|
mov bx,seg _Dorg_
|
|
mov es,bx ; Note well: BX now has _DATA's para #
|
|
;
|
|
; STACK SETUP
|
|
; -----------
|
|
; This code puts the stack in the uninitialized data area i.e., its
|
|
; eating up bytes in DGROUP. This is a necessary evil in the small
|
|
; data model, but in large data the stack can be anywhere you'd like.
|
|
;
|
|
; Note: Loading of SP must immediately follow the loading of SS
|
|
;
|
|
mov ss,bx
|
|
mov sp,offset cstack+stacksize shl 4
|
|
;
|
|
;
|
|
; COPY NEAR INITIALIZED DATA FROM ROM TO RAM
|
|
; ------------------------------
|
|
;
|
|
; This code assumes that the _DATA segment immediately follows
|
|
; the _TEXT segment in ROM (that is, _Dorg_==_Cend_), and needs
|
|
; to be relocated to its proper address in RAM.
|
|
; This copying might not be necessary. For example, if RDB downloads
|
|
; the .LOC file, it places _DATA at the correct address.
|
|
; To prevent this copying, equate the symbol NEAR_DATA_INIT to 0.
|
|
;
|
|
; ALOC guarantees that segment-bracket symbols will have the same
|
|
; paragraph address, and we take advantage of that here.
|
|
|
|
if NEAR_DATA_INIT
|
|
|
|
mov si,offset _Cend_ ; Get src addr into DS:SI
|
|
mov di,offset _Dorg_ ; Get dest addr into ES:DI
|
|
mov cx,offset _Dend_ ; Get # words to copy into CX
|
|
sub cx,di
|
|
mov dx,cx ; Get # bytes to copy into DX
|
|
shr cx,1
|
|
jcxz d00
|
|
|
|
rep movsw ; Copy the sucker
|
|
d00: ; ES:DI has addr of _Dend_
|
|
test dx,1 ; Odd number of bytes?
|
|
jz d10 ; Jump if not
|
|
movsb ; Copy the last byte
|
|
d10:
|
|
|
|
endif
|
|
|
|
; COPY FAR INITIALIZED DATA FROM ROM TO RAM
|
|
; -----------------------------------------
|
|
; To have the FAR_DATA class copied, equate FAR_DATA_INIT to 1.
|
|
;
|
|
if FAR_DATA_INIT
|
|
|
|
call far_init
|
|
|
|
endif
|
|
|
|
; CLEAR FAR UNINITIALIZED DATA SEGMENT
|
|
; ------------------------------------
|
|
; To have the FAR_BSS class cleared, equate FAR_BSS_INIT to 1.
|
|
;
|
|
if FAR_BSS_INIT
|
|
|
|
call far_clear
|
|
|
|
endif
|
|
|
|
|
|
;
|
|
; ZERO-OUT UNINITIALIZED DATA
|
|
; ---------------------------
|
|
; Clear uninitialized data. This step should always be performed, since
|
|
; C guarantees that uninitialized data will contain 0 upon startup.
|
|
;
|
|
mov di,offset _Uorg_ ; Get addr of _BSS seg into ES:DI
|
|
mov cx,offset _Uend_ ; Get # words to copy into CX
|
|
mov dx,cx ; Get # bytes to copy into DX
|
|
sub cx,di
|
|
shr cx,1
|
|
jcxz b00
|
|
sub ax,ax ; We're stuffing 0's in the BSS area
|
|
rep stosw ; Zero it out
|
|
b00:
|
|
test dx,1 ; Odd number of bytes?
|
|
jz b10 ; Jump if not
|
|
stosb ; Clear the last byte
|
|
b10:
|
|
;
|
|
assume ds:dataseg,es:dataseg
|
|
|
|
mov ds,bx ; BX has _DATA's para #, remember?
|
|
mov _dsval_,ds
|
|
mov _csval_,cs ;this is of dubious value in large code
|
|
|
|
;
|
|
; HEAP SETUP
|
|
; ----------
|
|
; This sets up various variables required by the memory allocation
|
|
; routines in the run-time library (malloc(), free(), etc.).
|
|
;
|
|
mov di,offset _Uend_
|
|
inc di
|
|
and di,0fffeH ;adjust to word boundary
|
|
mov _mcur_,di ;save memory allocation info for sbrk()
|
|
mov _mbot_,di
|
|
add di,heapsize shl 4
|
|
mov _mtop_,di
|
|
mov _sbot_,offset cstack
|
|
|
|
sti
|
|
call $fltinit ;setup floating point software/hardware
|
|
jnc flt_ok
|
|
hlt ;program needs 8087 and one wasn't found
|
|
flt_ok:
|
|
jmp main_ ;main usually doesn't return in ROM based system
|
|
$begin endp
|
|
;
|
|
; END OF $BEGIN
|
|
; -------------
|
|
|
|
if CPU_186
|
|
;----------------------------------------------------------------------------
|
|
;
|
|
; 80186 INITIALIZATION CODE
|
|
; -------------------------
|
|
; If your target system is an 8018X machine (80186, 80188, etc.), you
|
|
; will in most likelihood have to turn on your main ROM's memory chip
|
|
; select at the reset vector address (ffff:0). Sample code for doing
|
|
; this and then jumping to the entry point is provided here.
|
|
; REMEMBER, YOU HAVE ONLY 16 BYTES IN THE RESET_CODE SEGMENT!! So only
|
|
; perform absolutely necessary initializations here - all other
|
|
; initializations can be done within the $begin routine (such as
|
|
; additional chip selects).
|
|
;
|
|
; This example code sets the upper memory code select (UMCS) to be
|
|
; 8k wide. (i.e., it assumes you've got a 8K ROM at the top-most
|
|
; portion of the target's memory address space). If your ROM is a
|
|
; different size, use the appropriate MBS_X defintion (where 'x' is the
|
|
; size of your ROM, in kilobytes) for the ROM_SZ equate.
|
|
;
|
|
; Once the chip select is setup, it immediately jumps to the main
|
|
; initialization code at $begin.
|
|
;
|
|
;----------------------------------------------------------------------------
|
|
|
|
ROM_SZ equ MBS_8 ; Assume a 8K ROM.
|
|
|
|
RESET_CODE segment AT 0ffffh
|
|
mov dx,UMCS
|
|
mov ax,MBS_8
|
|
out dx,ax
|
|
jmp $begin
|
|
RESET_CODE ends
|
|
else
|
|
;----------------------------------------------------------------------------
|
|
; GENERIC 80x86 reset code
|
|
; ------------------------
|
|
; This is typical reset code for a non-80186/80188 system, where we
|
|
; simply jump to $begin.
|
|
;
|
|
; NOTE: There are only 16 bytes (that's bytes, not k-bytes!!) available
|
|
; in the RESET_CODE segment, so only absolutely necessary initialization
|
|
; should be done here. Most initializations should instead go into
|
|
; the $begin routine.
|
|
;----------------------------------------------------------------------------
|
|
RESET_CODE segment AT 0ffffh
|
|
jmp $begin
|
|
RESET_CODE ends
|
|
endif
|
|
|
|
;----------------------------------------------------------------------------
|
|
;FAR_INIT - Copy Far initialized data from ROM to RAM. ;
|
|
; ;
|
|
; On entry, ES:DI points at the first byte after the _DATA segment in ROM.
|
|
; By default, this is where AHEX places the program's FAR_DATA class. If
|
|
; FAR_DATA is somewhere else in ROM, this code will have to be changed.
|
|
;
|
|
; far_init makes no assumptions about the starting position of the source
|
|
; and destination blocks, or the length. This code could thus be optimized
|
|
; if assumptions can be made (such as length<64k, starting addrs on para
|
|
; boundary).
|
|
;----------------------------------------------------------------------------
|
|
|
|
if FAR_DATA_INIT
|
|
extrn _FDorg_:byte, _FDend_:byte
|
|
ifdef FARPROC
|
|
extrn _ptrdiff_:far
|
|
else
|
|
extrn _ptrdiff_:near
|
|
endif
|
|
|
|
far_init proc near
|
|
; Preserve regs...
|
|
push bx
|
|
push es
|
|
push ds
|
|
|
|
; Load registers for copy...
|
|
mov ax,seg _FDorg_ ; Get len of FAR_DATA into DX,CX
|
|
push ax
|
|
mov ax,offset _FDorg_
|
|
push ax
|
|
mov ax,seg _FDend_
|
|
push ax
|
|
mov ax,offset _FDend_
|
|
push ax
|
|
call _ptrdiff_
|
|
add sp,8
|
|
mov cx,ax
|
|
|
|
mov ax,es ; Get 'from' addr into DS:SI
|
|
mov ds,ax
|
|
mov si,di
|
|
|
|
mov ax,seg _FDorg_ ; Get 'to' addr into ES:DI
|
|
mov es,ax
|
|
mov di,offset _FDorg_
|
|
; Copy...
|
|
ch00:
|
|
movsb ;copy one byte
|
|
test si,si ;incr src para reg when necessary
|
|
jnz ch10
|
|
mov ax,ds
|
|
add ax,1000h
|
|
mov ds,ax
|
|
ch10:
|
|
test di,di ;incr dest para reg when necessary
|
|
jnz ch20
|
|
mov ax,es
|
|
add ax,1000h
|
|
mov es,ax
|
|
ch20:
|
|
add cx,-1 ;decr counter
|
|
adc dx,-1
|
|
mov ax,cx ;anything left to copy?
|
|
or ax,dx
|
|
jnz ch00 ;loop if yes
|
|
; Restore regs...
|
|
pop ds
|
|
pop es
|
|
pop bx
|
|
; Return to caller...
|
|
ret
|
|
|
|
far_init endp
|
|
|
|
|
|
|
|
endif
|
|
;
|
|
|
|
;----------------------------------------------------------------------------
|
|
;FAR_CLEAR - Clear far uninitialized data
|
|
;
|
|
; far_clear makes no assumptions about the starting position of the source
|
|
; and destination blocks, or the length. This code could thus be optimized
|
|
; if assumptions can be made (such as length<64k, starting addrs on para
|
|
; boundary).
|
|
;----------------------------------------------------------------------------
|
|
|
|
if FAR_BSS_INIT
|
|
extrn _FUorg_:byte, _FUend_:byte
|
|
ifdef FARPROC
|
|
extrn _ptrdiff_:far
|
|
else
|
|
extrn _ptrdiff_:near
|
|
endif
|
|
|
|
far_clear proc near
|
|
; Preserve regs...
|
|
push bx
|
|
push es
|
|
push ds
|
|
|
|
; Load registers for clear ...
|
|
mov ax,seg _FUorg_ ; Get len of FAR_BSS class into DX,CX
|
|
push ax
|
|
mov ax,offset _FUorg_
|
|
push ax
|
|
mov ax,seg _FUend_
|
|
push ax
|
|
mov ax,offset _FUend_
|
|
push ax
|
|
call _ptrdiff_
|
|
add sp,8
|
|
mov cx,ax
|
|
|
|
mov ax,seg _FUorg_ ; Get far bss addr into ES:DI
|
|
mov es,ax
|
|
mov di,offset _FUorg_
|
|
; Clear...
|
|
xor ax,ax
|
|
bh00:
|
|
stosb ;clear one byte
|
|
test di,di ;incr dest para reg when necessary
|
|
jnz bh20
|
|
mov bx,es
|
|
add bx,1000h
|
|
mov es,bx
|
|
bh20:
|
|
add cx,-1 ;decr counter
|
|
adc dx,-1
|
|
mov bx,cx ;anything left to copy?
|
|
or bx,dx
|
|
jnz bh00 ;loop if yes
|
|
; Restore regs...
|
|
pop ds
|
|
pop es
|
|
pop bx
|
|
; Return to caller...
|
|
ret
|
|
|
|
far_clear endp
|
|
|
|
endif
|
|
;
|
|
|
|
codeseg ends
|
|
|
|
;
|
|
; $begin is the default entry point. If for reason you wish to change
|
|
; this, provide the entry routine in this file, and replace the name
|
|
; '$begin' after the end keyword with the name of your routine.
|
|
;
|
|
end $begin
|