AMTS/Reischl/lst/SIO_V24_Echo_Poll.s
2018-03-18 03:02:44 +01:00

174 lines
8.4 KiB
ArmAsm

;******************************************************************************
;* Z80 Assembler program *
;* Josef Reisinger *
;* josef.reisinger@htl-hl.ac.at *
;* 10/07/2017 *
;******************************************************************************
; ---------------------------- 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
CR: EQU $0D
LF: EQU $0A
SPACE: EQU $20
;******************************************************************************
;* RESET HANDLER *
;* Function: Start Main Programm *
;******************************************************************************
ORG $0000
JP MAIN ; jump to Main program
;******************************************************************************
;* NMI HANDLER *
;* Handles NMI Interrupt Request *
;******************************************************************************
ORG $0066
LD HL,NMI_TEXT ; Send NMI to V24
CALL SIO_PUT_STRING
RETN
;******************************************************************************
;* MAIN PROGRAM *
;******************************************************************************
ORG $100
MAIN: DI ; Disable interrupt
LD SP,RAMTOP ; Set stack pointer
CALL PIO_INIT ; Init PIO (8255)
CALL CTC_INIT ; Initialize CTC Channel 1 for 9600 Baud (SIO Channel A)
CALL SIO_INIT ; Initialize SIO for character based transfer (9600,n,8,1)
LD HL,START_TEXT ; Send Welcome Text to V24
CALL SIO_PUT_STRING
_AGAIN: CALL SIO_GET_CHAR ; Wait for Character on V24
LD A,E ; Output Error to LED's
OUT (PIO_B),A
CALL SIO_PUT_CHAR ; Echo Character to V24
JP _AGAIN
;
;******************************************************************************
;* Initialize PIO (8255) *
;******************************************************************************
PIO_INIT: LD A,$99 ; Init PIO 8255 Control Word:
; PA0-PA7=IN (DIP SWITCHES)
; PB0-PB7=OUT (LEDS),
OUT (PIO_CON),A ; PC0-PC7=IN, Mode 0 Selection
RET
;******************************************************************************
;* Initialize CTC Channel 1 (SIO Channel A Clock) *
;******************************************************************************
CTC_INIT: LD A,$05 ; Init Timer Counter - Channel 1
OUT (CTC1),A ; for Baudrate 9600 (No Interrupt, Timer Mode, PSC=16,
; trigger on positive edge
LD A,$0C ; Write Time constant 12*16*552ns= 105,98s
OUT (CTC1),A
RET
;******************************************************************************
;* Initialize SIO Channel A for character based transfer *
;******************************************************************************
SIO_INIT: LD A,$30 ; Write to WR0 Register --> Error Reset
OUT (SIO_A_C),A
LD A,$18 ; Write to WR0 Register --> Channel Reset
OUT (SIO_A_C),A
LD A,$04 ; Select WR4 Register
OUT (SIO_A_C),A
LD A,$04 ; CLK*1, 1STOP Bit, No Parity
OUT (SIO_A_C),A
LD A,$03 ; Select WR3 Register
OUT (SIO_A_C),A
LD A,$C1 ; RX enable,8 Data Bits
OUT (SIO_A_C),A
LD A,$05 ; Select WR5 Register
OUT (SIO_A_C),A
LD A,$68 ; TX enable,8 Data Bits, DTR inactive, RTS inactive, Break off
OUT (SIO_A_C),A
LD A,$1 ; Select WR1 Register
OUT (SIO_A_C),A
LD A,$0 ; No Interrupts for Rx and Tx Characters
OUT (SIO_A_C),A
RET
;******************************************************************************
;* Send one Character Via SIO Channel A(Polling Mode) *
;* D- Register: Character to send (ASCII Code) *
;******************************************************************************
SIO_PUT_CHAR: PUSH AF
_TX_READY: IN A,(SIO_A_C) ; Read RRO Register
BIT 2,A ; TX Buffer empty ?
JP Z,_TX_READY ; No --> Wait
LD A,D ; load character in A
OUT (SIO_A_D),A ; Send character (Transfer Buffer)
POP AF
RET
;******************************************************************************
;* Receive one Character Via SIO Channel A(Polling Mode) *
;* D- Register: Character received (ASCII Code) *
;* E-Register: Error Code *
;******************************************************************************
SIO_GET_CHAR: PUSH AF
_RX_READY: IN A,(SIO_A_C) ; Read RRO Register
BIT 0,A ; RX Character Available ?
JP Z,_RX_READY ; No --> Wait
IN A,(SIO_A_D) ; Store character
LD D,A
LD A,$01 ; Select WR1 Register
OUT (SIO_A_C),A
IN A,(SIO_A_C) ; Read Error Register
LD E,A ; store Error Status
AND $70 ; only D6(CRC Framing Error),D5(Rx Overrun Error) und D4 (Parity Error)
JP Z,_RX_EXIT ; return if no error
LD A,$30 ; reset Error
OUT (SIO_A_C),A
_RX_EXIT: POP AF
RET
;******************************************************************************
;* SEND STRING to V24 via SIO *
;* HL: contains start address of string *
;******************************************************************************
SIO_PUT_STRING: PUSH AF
_NEXT_CHAR: LD A,(HL) ; get character
CP $00 ; END of String ?
JP Z,_TEXT_END
LD D,A
CALL SIO_PUT_CHAR ; send character
INC HL ; next character
JP _NEXT_CHAR
_TEXT_END: POP AF
RET
;******************************************************************************
;* TEXT DEFINITIONS *
;******************************************************************************
START_TEXT: DEFB CR,LF,'Z','8','0',SPACE,'D','E','M','O',SPACE,'V','1','.','0',$00
NMI_TEXT: DEFB CR,LF,'N','M','I',$00