As somebody elase said, I think you have to read the
data regiater too.
Ok, I improved my test program to read the data reg and also give some visual feedback:
LDAA #$10 ; like in JBUG
STAA $8008 ; ACIA control
STAA $8022 ; enable 1 digit leds
LOOP LDAA #$7F
STAA $8020 ; clear display
READ LDAA $8008 ; ACIA status
ASRA
BCC READ ; data ready?
LDAB $8009 ; ACIA data
STAA $8020 ; display status
LDX #$0100 ; delay
DELAY DEX
BNE DELAY
CMPB #'G ; EOT?
BNE LOOP
SWI
The idea is to light a digit for a brief period when a byte is read and have
the segments show the status register. Also it should exit if it received
the "G". Ok, the G may be *in* a data block but I hardly ever found a G
anyway.
At least it allows me to tune the volume until I receive something. But it looks
random and looking at the leds, like half of the bytes read are framing errors.
Obviously, I varied what I could think of (delay, "G", ...) used several
recorders (2PCs with audacity, a real cassette deck and two audio cables)
I assume you have the manual for this evaluation kit.
It's on bitsavers
if you don't. It explains how the cassette interface circuitry works in
some detail, and is well worth reading.
Yes, I have the manual and read it through.
I asusme you intiialising the 6850 correctly, and
that you're settign
that 4053 analoge switch properly,. If not, it can never work.
I'm initialising it by writing $10 in the control reg, which I copied from
the JBUG listing.
I don't find any reference of a "4053" or similar in the docs of the kit.
Do you have a (real [1]) tape recorder? If so, try
saving something.
Listen to the recording, does it sound like the typical 'burble'? And try
loading it. Point being if there's something wrong with how you're playing
the audio files you could have problems.
Yes, dug up my Realistic cassette recorder that came with my TRS-80 but it
didn't help.
The samples I'm trying to load are recorded with the kit itself. They sound
typical and I was able to decode them to binary. As a test, I decoded the
jbug rom and compared it to the file from bitsavers. It matched! (except for 4
bytes near the end which are zero on bitsavers an are actually different on
my rom). That made me conclude that the 'punch' function is working and the
samples I'm using are good. I would like to test with a known-good audio
file but I can't find any...
I must point out that the kit is expanded and I haven't figured out what it is
exactly. The wirewrap area on the processor board has two extra ACIAs and a
crystal. I understand the original was a 614.4, this seemed to be replaced
by 1MHz and the 614.4 used for the other ACIAs. Anyway, I already swapped
them (which did make me type less double characters since I guess the keyboard
scan delay is chosen for the original clock speed). The kit came with a Philips
Mini-DCR and the cables seem to be made to connect that on the J1 I/O connector.
I could go the route of restoring that, but it seems more challenging and
it wouldn't allow me to transfer data with the outside world.
But I'd like to get at least to the point that I can load and run a program without
having to type it in...
I also read that the kit allows to connect RS-232, that would be ideal but I don't
see how that's possible without adding components and wiring.
Wim.