Hi there,
I am currently trying to interface an old mass spectrometer (Balzers QMS-511 controller, if it matters) using a PCI-6509 board and SCB-100 connector box. The protocol calls for TTL signal over a 37 pins connector. Every 'line' consists of a pair of 'High pin' and 'Low pin'. There's 8 pairs (lets call them BD0-7) that are meant to be bidirectionnal and are dedicated to addressing (output) and data transfer (output and input). Other important pairs are the 'Strobe' (output), the 'Done' (input), and the 'Control' (output, two pairs).
Essentially, the protocol specifies that you begins by addressing a register. To do that, you put the 'BD0-7' pins in a certain state, lets say '01110101', then you set the 'Control' pairs to 'addressing state' (10). The next step is to put the 'Strobe' in the 'High' state and the spectrometer should acknowledge by driving the 'Done' pin to 'High', after which the 'Strobe' should be set to 'Low'. Then you can proceed to actually reading or writing data in the register using the 'BD0-7' pairs again through a similar succession of steps ('Set data on BD0-7 pairs if writing data' -> 'Set Control to Reading or Writing Data' -> 'Strobe High' -> 'Wait for Done' -> 'Read the data on the BD0-7 pairs if reading' -> 'Strobe Low').
The problem is that I am unable to switch the pairs BD0-7 (two ports of 8 lines) to input state after output. The pins stay in the same state the output left them. How can I correct this behaviour? Thanks for any help you may provide.
