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QRZ! Ham Radio 8
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QRZ Ham Radio Callsign Database - Volume 8.iso
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boot.asm
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Assembly Source File
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1992-04-28
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2KB
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62 lines
;*****************************************************************************
; This routine demonstrates how to construct a module which will boot
; from an external byte-wide EPROM and execute in on-chip Program RAM.
;
; The main routine simply toggles the least significant bit of Port-C
; and this activity can be monitored externally with an oscilloscope
; to confirm that the boot occurred correctly.
;
; assemble this routine with the following command line:
; asm56000 -a -b -l boot
;
; build the S-Record file for use by the PROM-Burner via the SREC utility:
; SREC boot
;
; The vectors will be placed into the EPROM at address $C000 and the
; main routine will start at $C0F0 in the EPROM.
;*****************************************************************************
m_pcc equ $FFE1 ;Port-C control register address (in X:)
m_pcddr equ $FFE3 ;Port-C data direction register
m_pcd equ $FFE5 ;Port-C data register
main equ $50 ;main routine starting address
RUNTIME equ 0 ;bootstrap into P:0
LOADTIME equ $C000 ;load into EPROM at P:$C000
page 132,66,3,3 ;format the page for 132 columns, 66 lines
org P:RUNTIME,P:LOADTIME
jsr <GO_1 ;RESET Vector...start program
nop ;...vectors have 2 words...
DUP 62 ;define unused vectors with
nop ;..."safe" default routine
nop
ENDM
org P:main,P:LOADTIME+(3*main)
GO_1
;**** simple routine to toggle I/O pin ****
movep #$0001,x:m_pcddr ;only lsb of Port-C will be an output
movep #$0000,x:m_pcc ;all Port-C pins will be G.P. I/O
_loop
bchg #0,x:m_pcd ;toggle the lsb of Port-C
jmp <_loop
CodeSize set *
;
; test to see if the code size exceeds the available on-chip resources
; (512 words in on-chip P:RAM)
;
IF CodeSize>$1FF
msg " WARNING WARNING WARNING WARNING WARNING"
msg "*** program size EXCEEDS onboard P:RAM ***"
msg " WARNING WARNING WARNING WARNING WARNING"
ENDIF
END