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c. Now, if any of the ports are to be set as outputs, you may set the values to that port with
the outputs still in the tristate condition. (If all ports are to be set as inputs, this step is not
necessary.)
d. If data bit D7 is low when the control byte is written, ONLY the associated buffer
controller is addressed. If, for example, a control byte of hex 80 has been sent as
previously described, and the data to be output are correct, and it is now desired to open
the three groups, then it is necessary to send a control byte of hex 00 to base address +3
to enable the Port 0 buffers. When you do this, the buffers will be enabled.
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
address +3.
Manual PCI-DIO-24DH
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