Manual PCI-DA12-8/16
19
At the same time, data bit D7 is also latched in the buffer controller. A high state puts the buffers in the
tristate mode; i.e., disabled. Now, if any of the ports are to be set as outputs, you may set the values of
the respective port with the outputs still in tristate condition. Lastly, to enable the ports a control byte with
bit D7 low must be sent to Base 23.
Note
All data bits except D7 must be the same for the two control bytes. Those buffers will now remain enabled
until another control byte with data bit D7 high is sent to Base 23.