121 lines
4.1 KiB
NASM
121 lines
4.1 KiB
NASM
; 6502 BIOS
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; Based on original code by Daryl Rictor
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; Adapted to Real Retro UART board for RC2014
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; Renamed to rruart.asm
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;
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; ----------------- assembly instructions ----------------------------
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;
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; this is a subroutine library only
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; it must be included in an executable source file
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;
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;
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;*** I/O Locations *******************************
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; Define the i/o address of the UART chip
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;*** Real Retro UART ************************
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uart_base = $c0c0
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uart_reg0 = $c0c0
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uart_reg1 = $c0c1
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uart_reg2 = $c0c2
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uart_reg3 = $c0c3
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uart_reg4 = $c0c4
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uart_reg5 = $c0c5
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uart_reg6 = $c0c6
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uart_reg7 = $c0c7
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uart_xmit = uart_reg0
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;uart_recv = $c040
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;uart_status = $c041
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;
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;***********************************************************************
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; UART I/O Support Routines
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;---------------------------------------------------------------------
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;
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uart_init
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lda #$80 ; Line control register, Set DLAB=1
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sta uart_reg3
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lda #$01 ; 115200 with 1.8432MHz; OSC / (16 * Baudrate)
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sta uart_reg0 ; Divisor latch
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lda #$00
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sta uart_reg1 ; Divisor latch
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LDA #$03 ; Line control register, 8N1, DLAB=0
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sta uart_reg3
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LDA #$02 ; Modem control register
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sta uart_reg4 ; Enable RTS
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LDA #$87 ; FIFO enable, reset RCVR/XMIT FIFO
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sta uart_reg2
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lda #$01 ; Enable receiver interrupt
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sta uart_reg1
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jsr AFE_16C550
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; Nothing to init
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IF 0
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ldx #4
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lda #$0a
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ui_loop
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jsr uart_output
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dex
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bne ui_loop
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lda #$0d
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jsr uart_output
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ldx #'1'
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eeee
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txa
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jsr uart_output
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inx
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jmp eeee
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ENDIF
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rts ; done
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;---------------------------------------------------------------------
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; Input char from UART (blocking)
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; Exit: character in A
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uart_input
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lda uart_reg5 ; Serial port status
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and #$01 ; is recvr full
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beq uart_input ; no char to get
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lda uart_reg0 ; get chr
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rts ;
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;---------------------------------------------------------------------
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; Non-waiting get character routine
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; Scan for input (no wait), C=1 char, C=0 no character
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uart_scan
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clc
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lda uart_reg5 ; Serial port status
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and #$01 ; mask rcvr full bit
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beq uart_scan2
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lda uart_reg0 ; get chr
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sec
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uart_scan2 rts
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;---------------------------------------------------------------------
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; output to OutPut Port
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; Entry: character in A
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; Exit: character in A
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uart_output
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pha ; save registers
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uart_out1
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lda uart_reg5 ; serial port status
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and #$20 ; is tx buffer empty
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beq uart_out1 ; no
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pla ; get chr
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sta uart_reg0 ; put character to Port
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rts ; done
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;---------------------------------------------------------------------
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AFE_16C550
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LDA #$87 ; Trigger level, FIFO enable, reset FIFO
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sta uart_reg2
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; Use this to enable autoflow control
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LDA #$22 ; Modem control register
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sta uart_reg4 ; Enable AFE
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rts
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;
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;end of file
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