Digital I/O Data Registers
VCM-DAS-3 Reference Manual
22
Digital I/O Data Registers
D
IGITAL
I
NPUT
R
EGISTERS
DIOA (Read) 0304h
D7
D6
D5
D4
D3
D2
D1
D0
DIO A7
DIO A6
DIO A5
DIO A4
DIO A3
DIO A2
DIO A1
DIO A0
DIOB (Read) 0305h
D7
D6
D5
D4
D3
D2
D1
D0
DIO B7
DIO B6
DIO B5
DIO B4
DIO B3
DIO B2
DIO B1
DIO B0
DIOC (Read) 0306h
D7
D6
D5
D4
D3
D2
D1
D0
DIO C7
DIO C6
DIO C5
DIO C4
DIO C3
DIO C2
DIO C1
DIO C0
Table 12: Digital Input Data Bit Assignments
Bit
Mnemonic
Description
7-0
DIO A7-A0
DIO B7-B0
DIO C7-C0
Digital Input Data
– Data read from these registers returns the current input
state of the digital port signals on connectors J1 and J2. Data is not inverted.
When a signal line is high, the bit reads as 1; when a signal line is low, the bit
reads as 0.
To operate a port in input mode, you must first set the direction of the port to
input by setting the appropriate bit in the DIOCTRL register. If a port is operated
in output mode, the registers can be used to read back the logic state of the
output lines. Normally, the data read would be the same as the data written to
the output registers; however, if an output line is stuck high or shorted to ground,
the fault will be reflected in the feedback data.