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gp2io
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Update README.md

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Charles Mangin 2016-07-20 16:28:54 -05:00 committed by GitHub
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README.md
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@ -301,8 +301,7 @@ The plan, again, is to mimic data coming in on the cassette port, but with the p
From Apple II Circuit Description by Winston Gaylor
©1983 by Howard and Sams & Co, Inc.
Here's the source for those calls, again via
https://github.com/cmosher01/Apple-II-Source/blob/master/src/system/monitor/common/cassette.m4
Here's the source for those calls, again via https://github.com/cmosher01/Apple-II-Source/blob/master/src/system/monitor/common/cassette.m4
TAPEOUT = $C020
TAPEIN = $C060
@ -338,6 +337,7 @@ $C05C = set annunciator 2 = 0
Entry point at $34A. Received byte is returned in Accumulator
READCOMBINED
034A- A2 09 LDX #$09 ; reading 8 bits requires 9 transitions.
034C- A9 00 LDA #$00 ; clear the accumulator
034E- 85 EF STA $EF ; $EF is staging for received byte, set 0
@ -363,6 +363,7 @@ READCOMBINED
And a demo: this reads one byte from the AVR output buffer to the screen. It gets one byte at a time, triggered by a keypress. The AVR will need to be ready to send one byte at a time when it sees ANN2 go HIGH ("SEND BUFFER CONTENT" mode, set by sending $80 as the function switch first).
GETBYTEONKEY
0800- 20 1B FD JSR $FD1B ; wait for keypress
0803- 20 4A 03 JSR $034A ; READBYTE
0806- 20 DA FD JSR $FDDA ; print hex to screen
@ -378,9 +379,7 @@ The GP2IO then sends the requested number of bytes from its internal output buff
Here is a buffered I/O routine for minimally interactive data transmission between the Apple II and a serial device connected to the GP2IO.
0800- 20 4D 08 JSR $084D ; start by querying the buffer length - is there anything waiting?
; returns with buffer length in $08
0800- 20 4D 08 JSR $084D ; start by querying the buffer length - is there anything waiting? returns with buffer length in $08
0804- A9 80 LDA #$80 ; load control byte $80 "send buffer bytes"
0806- 20 03 03 JSR $0303 ; send control byte
0809- A5 08 LDA $08 ; load buffer length (or however much buffer you want sent)
@ -394,11 +393,13 @@ Here is a buffered I/O routine for minimally interactive data transmission betwe
081D- A5 08 LDA $08 ; load Accumulator with new buffer length
0820- D0 EC BNE $080E ; if there's more to come, loop (betweenbytes)
0822- 20 8E FD JSR $FD8E ; last byte. print CF/LF
0825- 60 RTS ; return
0825- 60 RTS ; return
GETLINE
0826- 20 6A FD JSR $FD6A ; get line of input
0829- 8A TXA ; get input length into Accumulator
0829- 8A TXA ; get input length into Accumulator
082A- 85 07 STA $07 ; put input length into $07
082C- A9 00 LDA #$00 ; load zero into Accumulator
082E- 85 06 STA $06 ; put zero into $06, keyboard buffer pointer
@ -414,7 +415,7 @@ GETLINE
0846- A5 06 LDA $06 ; load buffer pointer into Accumulator
0848- C5 07 CMP $07 ; compare with message length
084A- D0 EE BNE $083A ; if not at end of message, loop to (keybuffer)
084C- 60 RTS ; return
084C- 60 RTS ; return
QUERY BUFFER LENGTH
returns buffer length in $08
@ -426,7 +427,7 @@ returns buffer length in $08
0858- 20 4A 03 JSR $034A ; CTS - ready for response byte with buffer length
085B- F0 F0 BEQ $084D ; if there's nothing in the buffer, loop until there is
085D- 85 08 STA $08 ; put the byte in $08
085F- 60 RTS ; return
085F- 60 RTS ; return