320
CHAPTER 17 SERIAL INTERFACE IIC0 (
µ
PD780344Y, 780354Y SUBSERIES ONLY)
User’s Manual U15798EJ2V0UD
17.5 I
2
C Bus Definitions and Control Methods
The following section describes the I
2
C bus’s serial data communication format and the signals used by the I
2
C
bus. Figure 17-8 shows the transfer timing for the “start condition”, “data”, and “stop condition” output via the I
2
C
bus’s serial data bus.
Figure 17-8. I
2
C Bus Serial Data Transfer Timing
1 to 7
8
9
1 to 7
8
9
1 to 7
8
9
SCL0
SDA0
Start
condition
Address
R/W
ACK
Data
Data
Stop
condition
ACK
ACK
The master device outputs the start condition, slave address, and stop condition.
The acknowledge signal (ACK) can be output by either the master or slave device (normally, it is output by the
device that receives 8-bit data).
The serial clock (SCL0) is continuously output by the master device. However, in the slave device, the SCL0’s
low level period can be extended and a wait can be inserted.
17.5.1 Start conditions
A start condition is met when the SCL0 pin is at high level and the SDA0 pin changes from high level to low level.
The start conditions for the SCL0 pin and SDA0 pin are signals that the master device outputs to the slave device
when starting a serial transfer. The slave device includes hardware for detecting start conditions.
Figure 17-9. Start Conditions
H
SCL0
SDA0
A start condition is output when bit 1 (STT0) of IIC control register 0 (IICC0) is set (1) after a stop condition has
been detected (SPD0: bit 0 = 1 in IIC status register 0 (IICS0)). When a start condition is detected, bit 1 of IICS0
(STD0) is set (1).
Содержание mPD780344 Series
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