Motorola M68EVB912B32, User Manual

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D-BUG12 STARTUP CODE
68EVB912B32UM/D C-2
;*****************************************************************************
**
; INITIALIZATION
;
; The code in this section is initialization for the monitor on the EVB12B32
;*****************************************************************************
**
__MonStartup:
lds #STACKTOP ; initialize monitor stack pointer
;
;
Disable the COP watchdog by CR2:CR 1:CR0 = 0:0:0
; COPCTL = $07 when reset in normal modes
; FCME and CRx bits are write once in normal modes
; COPCTL [ CME :FCME : FCM : FCOP ! DISR : CR2 : CR1 : CR0 ] $--16
;
clr COPCTL ; disable watchdog
;
;
Clear all monitor RAM to start from a known state
;
ldx #MonRAMStart
ClrRAM: clr 1,x+ ; clear one and inc pointer
cpx #MonRMonRAMSize
bne ClrRAM ; loop till RAM clear
; Enable pipe signals, E, low strobe and read/write in port E
; PIPOE, NECLK, LSTRE and RDWE are write once i n normal modes
; PEAR [ARSIE :CDLTE :PIPOE :NECLK !LSTRE : RDWE : 0 : 0 ] $--0A
;
ldaa #$2c ; prevent later protection lock
staa PEAR ; PROTLK is write-once
; Without changing modes, enable internal visibility
; MODE [SMODN : MODB : MODA : ESTR ! IVIS : 0 : EMD : EME ] $--0B
;
bset MODE,$08 ; set IVIS
; Enable EEPROM so monitor can program/erase bytes
; EEMCR [ 1 : 1 : 1 : 1 ! 1 : 1 :PROTLK: EERC ] $--F0
; BPROT [ 1 :BPROT6:BPROT5:BPROT4!BPROT3:BPROT2: BPROT1:BPROT0] $--F1
;
ldaa #$fc ; prevent later protection lock
staa EEMCR ; PROTLK is write-once
clr BPROT ; allow EE program and erase
;
;
Disable writing to the on-chip Flash EEPROM
; FEELCK [ 0 : 0 : 0 : 0 : 0 : 0 : 0 : LOCK] $--F4
;
ldaa #$01 ; write a 1 to the Flash LOCK bit to
; disable accidential reprogramming of
staa FEELCK ; the flash memory (where we’re located)
;
ldd EEBase ; get the user supplied base address of the
; on-chip EEPROM
oraa #1 ; make sure that the EEON bit remains set.
staa INITEE ; re-map the on-chip EEPROM.
;
ldd IOBase ; get the user supplied base address of the
; on-chip I/O registers