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M16C/28 Group
Under development Preliminary specification
Specifications in this manual are tentative and subject to change.
14.1.3 Special Mode 1 (I2C Bus mode) (UART2)
Rev.0.60 2004.02.01
page 177 of N
REJ09B0047-0060Z
14.1.3 Special Mode 1 (I2C Bus mode)(UART2)
II2C mode is provided for use as a simplified I2C interface compatible mode. Table 14.1.3.1 lists the
specifications of the I2C mode. Table 14.1.3.2 and 14.1.3.3 list the registers used in the I2C mode and the
register values set. Table 14.1.3.4 lists the I2C mode fuctions. Figure 14.1.3.1 shows the block diagram
for I2C mode. Figure 14.1.3.2 shows SCL2 timing.
As shown in Table 14.1.3.2, the microcomputer is placed in I2C mode by setting the SMD2 to SMD0 bits
to ‘0102’ and the IICM bit to “1”. Because SDA2 transmit output has a delay circuit attached, SDA output
does not change state until SCL2 goes low and remains stably low.
Table 14.1.3.1. I2C Bus Mode Specifications
Item
Specification
Transfer data format
Transfer data length: 8 bits
Transfer clock
During master
U2MR register’s CKDIR bit = “0” (internal clock) : fj/ 2(n+1)
fj = f1SIO, f2SIO, f8SIO, f32SIO. n: Setting value of U2BRG register
0016 to FF16
During slave
CKDIR bit = “1” (external clock) : Input from SCL pin
Transmission start condition
Before transmission can start, the following requirements must be met (Note 1)
_ The TE bit of U2C1 register= 1 (transmission enabled)
_ The TI bit of U2C1 register = 0 (data present in U2TB register)
Reception start condition
Before reception can start, the following requirements must be met (Note 1)
_ The RE bit of U2C1 register= 1 (reception enabled)
_ The TE bit of U2C1 register= 1 (transmission enabled)
_ The TI bit of U2C1 register= 0 (data present in the UiTB register)
When start or stop condition is detected, acknowledge undetected, and acknowledge
detected
Error detection
Overrun error (Note 2)
This error occurs if the serial I/O started receiving the next data before reading the
U2RB register and received the 8th bit of the next data
Select function
Arbitration lost
Timing at which the U2RB register’s ABT bit is updated can be selected
SDA digital delay
No digital delay or a delay of 2 to 8 U2BRG count source clock cycles selectable
Clock phase setting
With or without clock delay selectable
Note 1: When an external clock is selected, the conditions must be met while the external clock is in the
high state.
Note 2: If an overrun error occurs, the value of U2RB register will be indeterminate. The IR bit of S2RIC
register does not change.
Interrupt request
generation timing