I/O Registers
12.8.1 PTC6/SCTxD (Transmit Data)
The PTC6/SCTxD pin is the serial data (standard or infrared) output from the SCI transmitter. The IRSCI
shares the PTC6/SCTxD pin with port C. When the IRSCI is enabled, the PTC6/SCTxD pin is an output
regardless of the state of the DDRC6 bit in data direction register C (DDRC).
NOTE
The PTC6/SCTxD pin is an open-drain pin when configured as an output.
Therefore, when configured as SCTxD or a general purpose output pin
(PTC6), a pullup resistor must be connected to this pin.
12.8.2 PTC7/SCRxD (Receive Data)
The PTC7/SCRxD pin is the serial data input to the IRSCI receiver. The IRSCI shares the PTC7/SCRxD
pin with port C. When the IRSCI is enabled, the PTC7/SCRxD pin is an input regardless of the state of
the DDRC7 bit in data direction register C (DDRC).
NOTE
The PTC7/SCRxD pin is an open-drain pin when configured as an output.
Therefore, when configured as a general purpose output pin (PTC7), a
pullup resistor must be connected to this pin.
Table 12-5 shows a summary of I/O pin functions when the SCI is enabled.
Table 12-5. SCI Pin Functions (Standard and Infrared)
IRSCC1
[ENSCI]
IRSCIRCR
[IREN]
IRSCC2
[TE]
IRSCC2
[RE]
TxD Pin
RxD Pin
Hi-Z(1)
Hi-Z(1)
1
0
0
0
Input ignored (terminate externally)
1
1
1
1
0
0
0
1
0
1
1
0
1
0
1
0
Input sampled, pin should idle high
Input ignored (terminate externally)
Input sampled, pin should idle high
Input ignored (terminate externally)
Output SCI (idle high)
Output SCI (idle high)
Hi-Z(1)
Hi-Z(1)
1
1
1
0
1
1
1
X
0
1
1
X
1
0
1
X
Input sampled, pin should idle high
Input ignored (terminate externally)
Input sampled, pin should idle high
Output IR SCI (idle high)
Output IR SCI (idle high)
Pins under port control (standard I/O port)
1. After completion of transmission in progress.
12.9 I/O Registers
The following I/O registers control and monitor SCI operation:
•
•
•
IRSCI control register 1 (IRSCC1)
IRSCI control register 2 (IRSCC2)
IRSCI control register 3 (IRSCC3)
MC68HC908AP Family Data Sheet, Rev. 4
Freescale Semiconductor
197
FREESCALE [ Freescale ]
