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Better check for 6551

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This commit is contained in:
Colin Leroy-Mira 2023-10-09 10:48:01 +02:00
parent 2726192aaf
commit 037628a24f
1 changed files with 50 additions and 22 deletions
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72
libsrc/apple2/ser/a2.ssc.s
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@ -25,6 +25,8 @@
.include "ser-kernel.inc"
.include "ser-error.inc"
.importzp tmp1, tmp2
.macpack module
.macpack cpu
@ -141,35 +143,16 @@ ParityTable: ; Table used to translate RS232 parity param
.byte $A0 ; SER_PAR_MARK
.byte $E0 ; SER_PAR_SPACE
IdOfsTable: ; Table of bytes positions, used to check five
IdOfsTable: ; Table of bytes positions, used to check four
; specific bytes on the slot's firmware to make
; sure this is an SSC (or Apple //c comm port)
; firmware that drives an ACIA 6551 chip.
;
; The SSC firmware and the Apple //c(+) comm
; port firmware all begin with a BIT instruction.
; The IIgs, on the other hand, has a
; Zilog Z8530 chip and its firmware starts with
; a SEP instruction. We don't want to load this
; driver on the IIgs' serial port. We'll
; differentiate the firmware on this byte.
;
; The next four bytes we check are the Pascal
; Firmware Protocol Bytes that identify a
; serial card. Those are the same bytes for
; SSC firmwares, Apple //c firmwares and IIgs
; Zilog Z8530 firmwares - which is the reason
; we have to check for the firmware's first
; instruction too.
.byte $00 ; First instruction
; sure this is an SSC (or Apple //c comm port).
.byte $05 ; Pascal 1.0 ID byte
.byte $07 ; Pascal 1.0 ID byte
.byte $0B ; Pascal 1.1 generic signature byte
.byte $0C ; Device signature byte
IdValTable: ; Table of expected values for the five checked
IdValTable: ; Table of expected values for the four checked
; bytes
.byte $2C ; BIT
.byte $38 ; ID Byte 0 (from Pascal 1.0), fixed
.byte $18 ; ID Byte 1 (from Pascal 1.0), fixed
.byte $01 ; Generic signature for Pascal 1.1, fixed
@ -210,6 +193,48 @@ SER_CLOSE:
stx Index ; Mark port as closed
rts
;----------------------------------------------------------------------------
; Internal function to test whether we're really talking with a 6551,
; or at least it really looks like it.
; Input: X= Index
; Output: carry set if this is very probably a 6551, clear if not
Verify6551:
lda ACIA_STATUS,x ; Save current values in what we expect to be
pha ; the ACIA status register
lda ACIA_CMD,x ; and command register. So we can restore them
sta tmp1 ; if this isn't a 6551.
and #$01
bne NotAcia ; We expect command register bit 0 to be 0
lda tmp1
ora #$01 ; Enable receiver/transmitter
sta ACIA_CMD,x
sta tmp2 ; Store it for comparison
lda ACIA_CMD,x ; Is command register what we wrote?
cmp tmp2
bne NotAcia
sta ACIA_STATUS,x ; Reset Acia (value written is not important)
lda ACIA_CMD,x ; Is the value back to the original value?
cmp tmp1
bne NotAcia
pla ; Clear stack of leftovers
clc
rts
NotAcia:
lda tmp1 ; Restore saved bytes, they're probably needed
sta ACIA_CMD,x
pla
sta ACIA_STATUS,x
sec
rts
;----------------------------------------------------------------------------
; SER_OPEN: A pointer to a ser_params structure is passed in ptr1.
; Must return an SER_ERR_xx code in a/x.
@ -239,6 +264,9 @@ SER_OPEN:
.endif
tax
jsr Verify6551
bcs NoDev
; Check if the handshake setting is valid
ldy #SER_PARAMS::HANDSHAKE
lda (ptr1),y