Port C; Port Configuration; Figure 4-Control Words - SeaLevel PIO-24.PCI 8008 User Manual

Port C

Port C has the ability to be configured as two four bit ports. If both lower and upper nibbles are
configured 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.
Port C absolute addressing (when port C is split)
When reading, the input nibble will be returned on the corresponding upper or lower
nibble while the 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. These will be eight bit operations and it will up to the
programmer to keep track of the two four bit nibbles.
Port C relative addressing (when port C is split)
The input and output nibbles will each be treated as individual four bit ports.

Port Configuration:

Each eight-bit port can be configured as inputs or outputs. The API provides a set adapter state
call to access the control words. For this device, one control word is used.
Note: The control panel also allows you to configure the device. Your program can over ride the
control panel configuration when executed, but the control panel configuration will be the default
on power up. The default settings are based on the settings in the control panel application when
last changed and saved after re-booting.
Control Words
I/O Configuration
CWnD0 Port C1 lower nibble (bits 0-3)
CWnD1 Port B1
CWnD2
CWnD3 Port C1 upper nibble (bits 4-7)
CWnD4 Port A1
CWnD5
CWnD6
CWnD7
Sealevel Systems PIO-24.PCI
Technical Description
1 = input 0 = output
1 = input 0 = output
0 or 1 (no effect)
1 = input 0 = output
1 = input 0 = output
0 or 1 (no effect)
0 or 1 (no effect)
Always a 1

Figure 4-Control Words

1 on power up
1 on power up
1 on power up
1 on power up
Page 9