Infrared Serial Communications Interface Module (IRSCI)
The SCI allows full-duplex, asynchronous, NRZ serial communication between the MCU and remote
devices, including other MCUs. The transmitter and receiver of the SCI operate independently, although
they use the same baud rate generator. During normal operation, the CPU monitors the status of the SCI,
writes the data to be transmitted, and processes received data.
NOTE
For SCI operations, the IR sub-module is transparent to the SCI module.
Data at going out of the SCI transmitter and data going into the SCI receiver
is always in SCI format. It makes no difference to the SCI module whether
the IR sub-module is enabled or disabled.
NOTE
This SCI module is a standard HC08 SCI module with the following
modifications:
•
•
A control bit, CKS, is added to the SCI baud rate control register to select between two input clocks
for baud rate clock generation
The TXINV bit is removed from the SCI control register 1
12.5.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 12-6.
8-BIT DATA FORMAT
BIT M IN IRSCC1 CLEAR
PARITY
BIT
NEXT
START
BIT
START
BIT
STOP
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
9-BIT DATA FORMAT
BIT M IN IRSCC1 SET
PARITY
BIT
NEXT
START
BIT
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
STOP
BIT
Figure 12-6. SCI Data Formats
12.5.2 Transmitter
Figure 12-7 shows the structure of the SCI transmitter.
The baud rate clock source for the SCI can be selected by the CKS bit, in the SCI baud rate register (see
12.9.7 IRSCI Baud Rate Register).
12.5.2.1 Character Length
The transmitter can accommodate either 8-bit or 9-bit data. The state of the M bit in IRSCI control register
1 (IRSCC1) determines character length. When transmitting 9-bit data, bit T8 in IRSCI control register 3
(IRSCC3) is the ninth bit (bit 8).
MC68HC908AP Family Data Sheet, Rev. 4
186
Freescale Semiconductor
FREESCALE [ Freescale ]
