Hugo Holden
Veteran Member
Hello,
I have fitted an 8 bit ISA LAVA bidirectional parallel card to my IBM5155. I want to read 8 bit data into the computer for use in some BASIC computer programs. I have set the card to LPT1 and when I write to the address &H378 (for example with the Basic command OUT &H378,X where X is some number 0 to 255) the output works fine with the correct binary values on pins 2 to pins 9 of the parallel connector on the card, so the output side of things works fine.
Then when I put the card into "input mode" by writing to bit 5 of the register &H37A (with the Basic command OUT &H37A,32 ) the connector pins for the 8 data bits appear to go into a high impedance state and I can apply +5V or ground to any of them without the pins drawing any significant current. So all that is what it appears it should be.....
However when I apply some binary values to those 8 bit inputs on the connector, and go to read them and print them to the screen with the Basic command PRINT INP (&H378) the value returned to the screen is 255, regardless of the value on the 8 bits of the connector pins 2 to 9 (or D0 to D7). It is as though the connector pins in some way are not coupled with the register I'm reading, or is there another register I should be reading ?
Thanks for any help with this problem. (PS the card has the correct jumper settings for bidirectional operation and LPT1 jumper selected)
I have fitted an 8 bit ISA LAVA bidirectional parallel card to my IBM5155. I want to read 8 bit data into the computer for use in some BASIC computer programs. I have set the card to LPT1 and when I write to the address &H378 (for example with the Basic command OUT &H378,X where X is some number 0 to 255) the output works fine with the correct binary values on pins 2 to pins 9 of the parallel connector on the card, so the output side of things works fine.
Then when I put the card into "input mode" by writing to bit 5 of the register &H37A (with the Basic command OUT &H37A,32 ) the connector pins for the 8 data bits appear to go into a high impedance state and I can apply +5V or ground to any of them without the pins drawing any significant current. So all that is what it appears it should be.....
However when I apply some binary values to those 8 bit inputs on the connector, and go to read them and print them to the screen with the Basic command PRINT INP (&H378) the value returned to the screen is 255, regardless of the value on the 8 bits of the connector pins 2 to 9 (or D0 to D7). It is as though the connector pins in some way are not coupled with the register I'm reading, or is there another register I should be reading ?
Thanks for any help with this problem. (PS the card has the correct jumper settings for bidirectional operation and LPT1 jumper selected)