dougm@palomar.SanDiego.NCR.COM (Doug Marshall) (02/15/90)
Sorry to post this. I got mail delivery error. Anyway, this response is for
J_SCHULL@CORNELLC.cit.cornell.edu.
I have a Technical Reference manual for the IBM PC-1. It belongs to NCR, so I'm
holding on to it for posterity. Anyway, I will quote from it as I think it
says what you want to know.
"The cassette interface is controlled through software. An output from the
8253 timer controls the data to the cassette recorder through pin 5 of the
cassette DIN connector at the rear of the system board. The cassette input
data is read by an input port bit of the 8255A-5 programmable peripheral
interface (8255A-5 PPI). This data is received through pin 4 of the cassette
connector. Software algorithms are used to generate and read cassette data.
The cassette drive motor is controlled through pins 1 and 3 of the cassette
connector. The drive motor on/off switching is controlled by an 8255A-5 PPI
output-port bit (hex 61, bit 3). The 8255A-5 address and bit assignments
are defined in "I/O Address Map" earlier in this section.
A 2 X 2 Berg pin and a jumper are used on the cassette 'data out' line. The
jumper allows use of the 'data out' line as a 0.075 Vdc microphone input
when placed across the M and C pins of the Berg connector. A 0.68 Vdc
auxiliary input to the cassette recorder is available when the jumper is
placed across the A and C pins of the Berg connector. The "System Board
Component Diagram" shows the locations of the cassette Berg pins.
M A M A
-------------- --------------
| . . | | . . |
| I | | I |
| . . | | . . |
-------------- --------------
C C C C
Microphone Auxiliary
Input (0.075Vdc) Input (0.68Vdc)
Here is a diagram (as best I can do) that shows the pinouts of the 5-Pin
DIN connector for the cassette.
____
/3 1\
|5 4|
\_2_ /
Pins 3 and 1 are at the top. Pin 1 is the Motor Control signal and is defined
as "Common from Relay". Pin 2 is ground. Pin 3 is Motor Control 6 Vdc;
1A (Relay N.O.) Pin 4 is Data In and is defined as 500nA at +-13V - at 1,000
to 2,000 Baud. Pin 5 is Data Out (Microphone or auxiliary) and is defined as
250uA at 0.68 or 0.075 as defined by the jumper located on the system board.
So, it looks like port 61 bit 3 will give you the signal that you want. Hope
this helps. If I can be of any further assistance, please let me know.
Cheers!
-- Doug
----
Doug Marshall <Doug.Marshall@SanDiego.NCR.COM> * My humble opinions and
+1 619 485 3494 <...!ncr-sd!palomar!dougm> * and ideas are just that.
"All of us is smarter than each of us!"
----
Doug Marshall <Doug.Marshall@SanDiego.NCR.COM> * My humble opinions and
+1 619 485 3494 <...!ncr-sd!palomar!dougm> * ideas are just that.
"All of us is smarter than each of us!"