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7220 Group User’s Manual

2.8 Multi-master I2C-BUS interface

(3)

I2C clock control register (S2: address 00DB16)

The I2C clock control register (address 00DB16) is used to set ACK control, SCL mode and SCL

frequency.

s Bits 0 to 4: SCL frequency control bits (CCR0–CCR4)

These bits control the SCL frequency. Refer to “Table 2.8.4.”

s Bit 5: SCL mode specification bit (FAST MODE)

This bit specifies the SCL mode. When this bit is set to “0,” the standard clock mode is set. When

the bit is set to “1,” the high-speed clock mode is set.

s Bit 6: ACK bit (ACK BIT)

This bit sets the SDA status when an ACK clockV is generated. When this bit is set to “0,” the ACK

return mode is set and SDA goes to LOW at the occurrence of an ACK clock. When the bit is set

to “1,” the ACK non-return mode is set. The SDA is held in the HIGH status at the occurrence of

an ACK clock.

However, when the slave address matches the address data in the reception of address data at

ACK BIT = “0,” the SDA is automatically made LOW (ACK is returned). If there is a mismatch

between the slave address and the address data, the SDA is automatically made HIGH (ACK is

not returned).

VACK clock: Clock for acknowledgment

s Bit 7: ACK clock bit (ACK)

This bit specifies a mode of acknowledgment which is an acknowledgment response of data

transmission. When this bit is set to “0,” the no ACK clock mode is set. In this case, no ACK clock

occurs after data transmission. When the bit is set to “1,” the ACK clock mode is set and the

master generates an ACK clock upon completion of each 1-byte data transmission. The device for

transmitting address data and control data releases the SDA at the occurrence of an ACK clock

(make SDA HIGH) and receives the ACK bit generated by the data receiving device.

Figure 2.8.4 shows the I2C clock control register.

Note: Do not write data into the I2C clock control register during transmission. If data is written during

transmission, the I2C clock generator is reset, so that data cannot be transmitted normally.

FUNCTIONAL DESCRIPTION

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