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timer
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1998-07-24
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1KB
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63 lines
; timer.s
; -------
; PC Engine timer emulation
; by Paul Clifford
;
; Started 16 August 1997
; ------------------------------------------------------------------------
AREA |timer$$code|, CODE, READONLY
; void Timer_Write(uhalf address, ubyte value)
; Timer write port
Timer_Write
EXPORT Timer_Write
cmp r0, #1
movgts pc, r14
ldrlt r2, adrof_timer_load
ldreq r2, adrof_timer_status
andlt r1, r1, #0x7f
andeq r1, r1, #1
str r1, [r2, #0]
movs pc, r14
; ubyte Timer_Read(uhalf address)
; Timer read port
Timer_Read
EXPORT Timer_Read
cmp r0, #1
ldrlt r1, adrof_timer_value
ldreq r1, adrof_timer_status
movgt r0, #0
ldrle r0, [r1, #0]
movs pc, r14
adrof_timer_value
DCD timer_value
adrof_timer_status
DCD timer_status
adrof_timer_load
DCD timer_load
; ------------------------------------------------------------------------
AREA |timer$$data|, DATA
timer_value
EXPORT timer_value
DCD 0x7f
timer_status
EXPORT timer_status
DCD 0
timer_load
EXPORT timer_load
DCD 0x7f
END