ADC-44D Datasheet, PDF (28/66 Pages) List of Unclassifed Manufacturers – Multi-Function Analogue Input/Output Card

Page 20
Operation of the Card
Chapter 5
OPERATION OF THE CARD
Programmable Digital Input Output
The ADC44d includes an NEC µPD71055 device which is equivalent to an Intel
i8255 PIO.
This device provides 24 programmable digital I/O channels. It is suitable for
sensing the presence of, or driving TTL connections only.
The digital I/O appears to the PC as four ports. The first three can be set as
input or output by writing suitable codes to the fourth Control Port.
These four ports are mapped into the ADC44d port map as follows:
ADDRESS
Base + 8
Base + 9
Base + 10
Base + 11
PORT
Programmable Digital I/O Port A
Programmable Digital I/O Port B
Programmable Digital I/O Port C
Control Port
READ/WRITE
R/W
R/W
R/W
W
A typical sequence of events to use this feature would be :
• Decide on the input/output mix and write the appropriate code to
BASE + 11.
• Read from the selected output port or write to the selected output port.