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XC2200 Derivatives
System Units (Vol. 1 of 2)
Parallel Ports
User’s Manual
7-14
V2.1, 2008-08
Parallel Ports, V1.6D6
Coding of the PC bit field
The coding of the GPIO port behavior is done by the bit fields in the port control registers
Pn_IOCRx. There’s a control bit field PC for each port pin. The bit fields PC are located
in separate control registers in order to allow modifying a port pin (without influencing the
others) with simple move operations.
Note: When the pin direction is switched to output and the mode is test mode, the output
characteristic must be push-pull only.
Field
Bits
Type Description
PC
[7:4]
rw
Port Input/Output Control Bit
0
[3:0],
[15:8]
r
reserved
Table 7-4
PC Coding
PC[3:0]
I/O
Selected Pull-up/down /
Selected Output Function
Behavior in Power Saving
Mode
1)
0000
B
Direct
Input
No pull device connected
Input value = Pn_OUT.x; no pull
0001
B
Pull-down device connected Input value = 0; pull-down
0010
B
Pull-up device connected
Input value = 1; pull-up
0011
B
No pull device connected.
Bit Pn_OUT.x reflects the
current input value
Input value = Pn_OUT.x; no pull
Pn_OUT.x contains the input value
before entering in power save
mode = freeze of input value
0100
B
Inverted
Input
No pull device connected
Input value = Pn_OUT; no pull
0101
B
Pull-down device connected Input value = 1; pull-down
0110
B
Pull-up device connected
Input value = 0; pull-up
0111
B
No pull device connected
Bit Pn_OUT.x reflects the
current input value
Input value = Pn_OUT; no pull
Pn_OUT.x contains the input value
before entering in power save
mode = freeze of input value
2)