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M16C/28 Group
Under development Preliminary specification
Specifications in this manual are tentative and subject to change.
16. MULTI-MASTER I2C bus INTERFACE
Rev.0.60 2004.02.01
page 247 of N
REJ09B0047-0060Z
16.3 I2C0 Clock Control Register (S20 register)
The I2C0 clock control register (address 02E416) is used to set theACK control, SCL mode and the SCL
frequency.
16.3.1 Bits 0 to 4: SCL frequency control bits (CCR0–CCR4)
These bits control the SCL frequency. See Table 16.3 Set values of I2C0 clock control register and
SCL frequency.
16.3.2 Bit 5: SCL mode specification bit (FAST MODE)
This bit specifies SCL mode. When this bit is set to “0”, Standard clock mode is selected. When the bit is
set to “1” , high-speed clock mode is selected. When connecting to the bus with high-speed mode I2C bus
standard (maximum 400 kbits/s), set 4 MHz or more to the I2C system clock(VIIC).
16.3.3 Bit 6: ACK bit (ACK BIT)
This bit sets the SDA status when an ACK clock(Note 1) is generated. When this bit is set to “0”, ACK return
mode is selected and the SDA goes to “L” at the ACK clock generation. When the bit is set to “1”, ACK non-
return mode is selected. The SDA is held in the “H” status at the ACK clock generation. However,
when the address data is received at the ACK BIT=0 and the slave address matches with the address data,
the SDA is automatically set to “L” (ACK is returned). If the slave address does not match with the address
data, the SDA is automatically set to “H” (ACK is not returned).
Note 1. ACK clock: Clock for acknowledgment
16.3.4 Bit 7: ACK clock bit (ACK)
This bit specifies mode of acknowledgment for responses to transfer data. When this bit is set to “0”, no
ACK clock mode is selected. In this case, the ACK clock is not generated after the data transmit. When
the bit is set to “1”, ACK clock mode is selected and the master generates an ACK clock at the completion
of each 1-byte data transfer. The device for transmitting the address data and the control data releases the
SDA at the ACK clock generation (set the SDA to “H”) and receives the ACK bit generated by the data receive
device.
Note . Do not rewrite the data into the I2C0 clock control register other than the ACK bit (ACKBIT) during
the transfer. If data is written during the transfer, the I2C Bus clock circuit is reset and the data can
not be transferred normally.