Technical Description
OMG-PCI-DIO48 Page 16
Port CPort C is written and read to as a single eight bit port, but it has the ability to be configured as two
four bit ports. If both lower and upper nibbles are configure the same then no special
considerations need to be made. But if they are configured differently, one nibble as input, and one
as output then the user will have to keep this in mind. When reading, the input will be returned on
the corresponding upper or lower nibble while the current outputs will be returned on their
corresponding upper or lower nibble. When writing, the corresponding nibble will be written to the
output nibble, while the input nibble will have its output register written to. The output register
can be written to without affecting the inputs.
Register Description (for direct hardware control)Address
Mode D7 D6 D5 D4 D3 D2 D1 D0
Base+0
Port A1 RD/WR
PA1D7
PA1D6
PA1D5
PA1D4 PA1D3
PA1D2
PA1D1
PA1D0
Base+1
Port B1 RD/WR
PB1D7
PB1D6
PB1D5
PB1D4 PB1D3 PB1D2
PB1D1
PB1D0
Base+2
Port C1 RD/WR
PC1D7
PC1D6
PC1D5
PC1D4 PC1D3 PC1D2
PC1D1
PC1D0
Base+3
Control Word
Port 1
WR CW1D7
0 0 CW1D4
CW1D3
CW1D2
CW1D1
CW1D0
Base+4
Interrupt
configuration
Port 1
RD/WR
0 0 0 0 0 IRQEN1
IRQC11
IRQC10
Base+5
Interrupt
status for
Port 1 and 2
RD 0 0 0 IRQST2
0 0 0 IRQST1
Port 2
Base+8
Port A2
RD/WR
PA2D7
PA2D6
PA2D5
PA2D4 PA2D3
PA2D2
PA2D1
PA2D0
Base+9
Port B2
RD/WR
PB2D7
PB2D6
PB2D5
PB2D4 PB2D3 PB2D2
PB2D1
PB2D0
Base+A
(10) Port C2
RD/WR
PC2D7
PC2D6
PC2D5
PC2D4 PC2D3 PC2D2
PC2D1
PC2D0
Base+B
(11)
Control Word
Port 2
WR CW2D7
0 0 CW2D4
CW2D3
CW2D2
CW2D1
CW2D0
Base+C
(12) Interrupt
configuration
Port 2
RD/WR
0 0 0 0 0 IRQEN2
IRQC21
IRQC20