AMTS/Reischl/lst/CTC_BLINKY_Interrupt.s
2018-03-18 03:02:44 +01:00

91 lines
4.5 KiB
ArmAsm

;******************************************************************************
;* Z80 Assemblerprogramm *
;* Josef Reisinger *
;* josef.reisinger@htl-hl.ac.at *
;* 26/04/2015 *
;******************************************************************************
; ---------------------------- PIO 82C55 I/O ---------------------------------
PIO_A: EQU $80 ; (INPUT)
PIO_B: EQU $81 ; (OUTPUT) OUT TO LEDS
PIO_C: EQU $82 ; (INPUT) IN from DIP SWITCHES
PIO_CON: EQU $83 ; CONTROL BYTE PIO 82C55
; --------------------------- CTC Z80 Timer Counter --------------------------
CTC0 EQU $00 ; Channel 0
CTC1 EQU $01 ; Channel 1
CTC2 EQU $02 ; Channel 2
CTC3 EQU $03 ; Channel 3
; -------------------------- SIO (USART) ----------------------------------------
SIO_A_D: EQU $40 ; Channel A Data Register
SIO_B_D: EQU $41 ; Channel B Data Register
SIO_A_C: EQU $42 ; Channel A Control Register
SIO_B_C: EQU $43 ; Channel B Control Register
;-------------------------- CONSTANTS ----------------------------------------
RAMTOP: EQU $FFFF ; 32Kb RAM 8000H-FFFFH
COUNTER: EQU $8000 ; RAM Counter
;******************************************************************************
;* RESET HANDLER *
;* Function: Initalize system and start Main Programm *
;******************************************************************************
ORG $0000
DI ; Disable interrupt
LD SP,RAMTOP ; Set stack pointer
JP MAIN ; jump to Main program
;*******************************************************************
;* MAIN PROGRAM *
;*******************************************************************
ORG $0100
MAIN: LD HL,COUNTER ; Reset RAM Counter
LD A,$00
LD (HL),A
; ------------------ Initialize PIO ----------------
LD A,$99 ; Initialize 8255: PA0-PA7=IN (DIP SWITCHES), PB0-PB7=OUT (LEDS),
OUT (PIO_CON),A ; PC0-PC7=IN, Mode 0 Selektion
;------------------ Configure CTC -----------------------
LD A,$A5 ; Configure CTC Channel 0:Interrupt, Timer Mode, Prescaler = 256,
OUT (CTC0),A ; trigger on positive edge, next word = time constant, Channel continuous result operation
LD A,$FF ; Write Time constant 255*256*552ns= 36,03ms
OUT (CTC0),A
LD A,$A8 ; Loading Interrupt Vector register
OUT (CTC0),A ; trigger on positive edge, next word = time constant, Channel continuous result operation
;---------------------- Configure Interrupt -----------------
LD A,$01 ; Loading Interrupt Register
LD I,A
IM 2 ; Interrupt Mode 2
EI ; Enable Interrupt
;--------------------- Main Program --------------------------
AGAIN: JP AGAIN ; Endlos
;******************************************************************************
;* INTERRUPT SERVICE ROUTINE *
;* CTC Channel 0 *
;******************************************************************************
ORG $01A8
DEFW _INT_CTC
_INT_CTC: PUSH AF
PUSH HL
LD HL,COUNTER
LD A,(HL) ; Read Counter
INC A ; Increment Counter
CP $07 ; 252,21ms reached?
JP NZ,_END_INT
LD A,$00 ; Reset Counter
IN A,(PIO_B) ; Toggle LED's with 2Hz
CPL
OUT (PIO_B),A ;
_END_INT: LD (HL),A ; Store Counter
POP HL
POP AF
EI ; Entry Point of Interrupt Service Routine
RETI