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CHAPTER 17 SERIAL INTERFACE CHANNEL 1
Figure 17-7. Transfer Bit Sequence Select Circuit
Read/write gate
Read/write gate
Shift register 1 (SIO1)
D
Q
7
6
Internal bus
1
0
LSB first
MSB first
SI1
SO1
SCK1
SO1 latch
The first bit to be transferred is selected by changing the bit sequence in which data is written to SIO1. The shift
sequence of SIO1 is unchanged.
Therefore, select the first bit to be transferred (MSB or LSB) before writing data to the shift register.
(4) Starting transfer
Serial transfer is started by placing transfer data in serial I/O shift register 1 (SIO1) if the following two conditions
are atisfied:
Serial interface channel 1 operation control bit (CSIE1) = 1
The internal serial clock is stopped or SCK1 is high after 8-bit serial data has been transferred
Caution
If CSIE1 is set to “1” after data has been written to SIO1, the transfer is not started.
Serial transfer is automatically stopped and an interrupt request flag (CSIIF1) is set after 8 bits of data have
been transferred.
17.4.3 Operation in 3-wire serial I/O mode with automatic transmit/receive function
This 3-wire serial I/O mode is to transmit/receive data of up to 32 bytes without intervention by software. When
transfer is started, data stored in RAM in advance can be transmitted by the set number of bytes, or data can be
received by the set number of bytes and stored in RAM.
To transmit/receive data successively, handshake signals (STB and BUSY) are supported by hardware, so that
OSD (On Screen Display) LSIs and peripheral LSIs such as LCD controllers/drivers can be easily connected.
(1) Register setting
The 3-wire serial I/O mode with automatic transmit/receive function is set by using the serial operation mode
register 1 (CSIM1) and automatic data transmit/receive control register (ADTC) and automatic data transmit/
receive interval specification register (ADTI).
(a) Serial operation mode register 1 (CSIM1)
CSIM1 is set by a 1-bit or 8-bit memory manipulation instruction.
This register is set to 00H when the RESET signal is input.