TKSA ORed the accumulator with $90 before sending it. Its callers pass
the secondary address plus $60, as the routine's own comment asks, so
TKSA turned a TALK secondary address $60-$6F into $F0-$FF, the OPEN
command, on the bus.
The contract (C64 Programmer's Reference Guide, TKSA; Michael Steil,
"Commodore Peripheral Bus: Part 2", https://www.pagetable.com/?p=1031,
which gives TKSA's argument as A = $60 + secondary address): TKSA sends
the byte in A as the secondary address to the device told to TALK.
TKSA now sends A as it is.
Upstream: https://github.com/MEGA65/open-roms/issues/116 (bug 1)
chkin_iec and ckout_iec read the secondary address from LAT, the table
of logical file numbers, instead of SAT, the table of secondary
addresses. A file whose number differed from its secondary address,
such as OPEN 3,8,2, was read from or written to the wrong channel, and
the read-only and write-only checks tested the file number.
The contract (Michael Steil, "Commodore Peripheral Bus: Part 2",
https://www.pagetable.com/?p=1031): CHKIN sends TALK and CHKOUT sends
LISTEN, each followed by the secondary address OPEN was given; Compute!'s
Mapping the Commodore 64 (p. 52) keeps the logical file numbers at
$0259 (LAT) and the secondary addresses at $026D (SAT). Both routines
now read SAT.
Not reported upstream (https://github.com/MEGA65/open-roms); it may be
what upstream issue #117's OPEN 1,8,0,"$" test met:
https://github.com/MEGA65/open-roms/issues/117
close_iec sent its CLOSE command under ATN without first addressing the
device with LISTEN and without UNLISTEN after it, and built the command
with ORA $E0 (zero page) instead of ORA #$E0, so the byte it sent was
the secondary address ORed with whatever $E0 held. The drive never
learned of the CLOSE, so a file written on a channel was never written
to the disk.
The contract (Michael Steil, "Commodore Peripheral Bus: Part 2",
https://www.pagetable.com/?p=1031): CLOSE of a file on a serial device
sends LISTEN, then $E0 plus the secondary address, then UNLISTEN.
close_iec now does that, as iec_close_load already does for LOAD.
Not reported upstream (https://github.com/MEGA65/open-roms).
CIOUT kept the byte to send next in BSOUR ($95), but iec_tx_byte, which
CIOUT and iec_tx_flush (called by UNLSN, UNTLK, LISTEN, TALK) use to
send it, transmits TBTCNT ($A4). So every byte CHROUT sent to a serial
device was whatever TBTCNT held, and a file written with CHKOUT and
CHROUT held the wrong bytes.
The contract (C64 Programmer's Reference Guide, CIOUT): CIOUT sends a
byte to the listening device, always holding one back so that the last
byte goes with EOI when UNLSN ends the transfer. CIOUT now buffers the
byte in TBTCNT, the one-line fix of upstream PR #113; changing the send
path to read BSOUR would also move LOAD's and SAVE's bytes.
Upstream: https://github.com/MEGA65/open-roms/pull/113
A copy of the c64 configuration with its own ID ($6D), the brand "MC64",
and BCD_SAFE_INTERRUPTS off, plus its Makefile targets
build/kernal_mc64.rom and build/basic_mc64.rom, made the same way as the
c64 ones. NOTICE says who modified the fork, when, and what changed.
chris