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Manual MPAD128.D1g
For example, if the point list held channels 3, 5,and 7, bits DF-DD for channel 3 would
hold 000, for channel 5 would hold 001, and for channel 7 would hold 010.
If SIGN mode is set, bits DF-DD are the sign-extension of the data, and hold the same
value as bit DC.
Bit DC is the sign bit. 0 is positive, 1 is negative.
Bits DB through D0 are the conversion data.
Note: If SIGN mode is set, the data is returned in 16-bit two's complement format. If
CH mode is set, some processing will be necessary to interpret the data.
Reading this base address as many times as indicated in Bits DF-DB of Base+14 will
grab the conversion results from the card.
Base A 20, Digital I/O 8255 Port A
D7 D6 D5 D4 D3 D2 D1 D0
DIO7 DIO6 DIO5 DIO4 DIO3 DIO2 DIO1 DIO0
This port contains DIO0 through DIO7's control and status bits.
Base A 21, Digital I/O 8255 Port B
D7 D6 D5 D4 D3 D2 D1 D0
DIO15 DIO14 DIO13 DIO12 DIO11 DIO10 DIO9 DIO8
This port contains DIO15 through DIO8's control and status bits.
Base A 22, Unused 8255 Port C
Base A 23, Digital I/O 8255 Control Register
D7 D6 D5 D4 D3 D2 D1 D0
M S M 2 M 1 A X M 0 B X
The control register at base a23 is a write-only 8-bit register. It is used to set
the mode and direction of the ports. At Power-Up or Reset, all I/O lines are set as
inputs. The PPI should be configured during initializing by writing to the control
register even if the ports are only going to be used as inputs. Bit assignments in the
control register are as follows:
Bit D7, MS, indicates an active mode set. Normally this will be set to 1 each time you
write to this register. If MS is 0, the chip will ignore the write.
Bits D6, D5, and D2 set the mode of operation: