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MODEM Boot Test / Card Select Pin B13
Posted: Sat Mar 07, 2020 10:11 am
by Chuckphd53
Has anyone looked at the Bios for the JR Modem ?
At boot, it will report an error 'E' if there is an issue with the modem
before I spend time on the bios, I am curious what generates this 'E' error...
My serial card for the modem slot does not like the CARD INSTALLED pin B13 to be active.
So I am guessing the boot inspection is looking for a loopback write/read of some sort to the Modem
I will delve into this if no one has any experience here..
Chuck
Re: MODEM Boot Test / Card Select Pin B13
Posted: Mon Mar 09, 2020 3:39 pm
by DoctorOctal
Looking at the BIOS code, I see this: The POST has a UART test routine for the internal serial port. If the modem slot’s CARD INSTALL on B13 indicates that a modem is installed, the POST will run the same routine on the modem’s UART. (
Tech Ref A-20)
The comment block on the UART test routine (Tech Ref A-56) summarizes the tests done. You’ll get a POST error “E” if any of them fails. In
service mode you’ll get a more precise error code.
Re: MODEM Boot Test / Card Select Pin B13
Posted: Mon Mar 09, 2020 4:36 pm
by Chuckphd53
That is correct, I went thru the UART code a few nights back and found it throws the 'E" code, but only when it has the B13 pin grounded as per the Jr specs..
My question was, there is a note on pg A66 bottom talking about the differences in the 8250 chips in that era that seemed to be INTR sensitive.
I am using a current day UART and I do get the 'E" failure, ie. it is setting the CARRY BIT to indicate the modem has failed.
Tonight I tested the Serial card installed NO B13 (taped over it, so the bios would not see a modem plugged in) and Dialed up a couple
2400baud BBS's with my external Hayes modem on COM1 using my card.
All worked well... I used Qmodem 5
I would like to understand what the bios is thinking about the interrupts on the NEW uart chip that is different from the
old 8250 chips,,,, has something to do with the Register Interrupt setting....
I have only spent a minimal time on the UART code, as most of us dont have alot of play time, but if someone is interested
in brushing up on their Assmbly code skills from long ago and reviewing this code it would be a nice little project to fully understand
that B13 pin issue....
but it is nice now to have a Mouse on the Back port COM2 for Turbo Pascal7 and A fully functional serial port COM1 for an external modem...
Chuck
Re: MODEM Boot Test / Card Select Pin B13
Posted: Mon Mar 09, 2020 5:48 pm
by DoctorOctal
Boot the machine in service mode using the service plug (if you have one) or
joystick buttons. That will give you a better error code to help narrow down the difference between the 8250's behavior and the behavior of whatever you’re using (16550D?). You’ll be able to see what part of the POST UART routine is running into a problem.
Quoting from the
diagnostics document:
Code: Select all
MANUFACTURING ERROR CODE SERVICE CODE CUSTOMER LEVEL CODE
------------------------ ------------ -------------------
EF24XX (FVT/PFT TESTER) 24XX E
EE24XX (BURN-IN/RUN-IN) ---- ---
------
MODEM 8250 ERROR
Code: Select all
XX=02 BITS THAT SHOULD ALWAYS BE "0" IN 8250 INT. ENABLE REG. WERE "ON"
XX=03 BITS THAT SHOULD ALWAYS BE "0" IN 8250 INT. I/D REG. WERE "ON"
XX=04 BITS THAT SHOULD ALWAYS BE "0" IN 8250 DATA SET CONTROL REG. WERE "ON"
XX=05 BITS THAT SHOULD ALWAYS BE "0" IN 8250 LINE STATUS REG. WERE "ON"
XX=06 RECEIVED DATA AVAILABLE INTERRUPT STATUS NOT PRESENTED FROM 8250
XX=16 RECEIVED DATA AVAILABLE INTERRUPT STATUS COULD NOT BE CLEARED
XX=17 TRANSMITTER HOLDING REG. INTERRUPT STATUS COULD NOT BE CLEARED
XX=08-0B RECEIVER LINE STATUS INTERRUPT COULD NOT BE GENERATED IN 8250
08=OVERRUN ERROR
09=PARITY ERROR
0A=FRAMING ERROR
0B=BREAK INTERRUPT
XX=18-1B RECEIVER LINE STATUS INTERRUPT COULD NOT BE CLEARED IN 8250
XX=0C-0F MODEM STATUS INTERRUPT COULD NOT BE GENERATED
0C=DELTA CLEAR TO SEND
0D=DELTA DATA SET READY
0E=RING INDICATE
0F=DELTA RECEIVE LINE SIGNAL DETECT
XX=1C-1F COULD NOT RESET MODEM STATUS INTERRUPT IN 8250
****NOTE***** THE "INTERRUPTS" NOTED IN THE ERRORS ABOVE ARE INTERNAL STATUS
BITS IN THE 8250. THEY HAVE NOTHING TO DO WITH THE SYSTEM 8259
INTERRUPT CHIP.
XX=10 SYSTEM INTERRUPT (8259) FROM 8250 FAILED
XX=11 TRANSMIT HOLDING REGISTER EMPTY DID NOT OCCUR DURING WRAP TEST
XX=12 RECEIVED DATA AVAILABLE DID NOT OCCUR DURING WRAP TEST
XX=13 TRANSMIT DATA NOT EQUAL TO RECEIVED DATA IN WRAP TEST
XX=14 DATA SET CTL.OUTPUTS NOT EQUAL TO DATA SET CTL.INPUTS IN WRAP MODE
XX=15 TRANSMITTER NOT IDLE AFTER WRAP TEST
Re: MODEM Boot Test / Card Select Pin B13
Posted: Mon Mar 09, 2020 11:20 pm
by Chuckphd53
Ah... this is good, will try tonight and report back.
much appreciation..