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7220 Group User’s Manual

2.8 Multi-master I2C-BUS interface

(4)

I2C Control Register (S1D: address 00DA16)

The I2C control register (address 00DA16) controls the data communication format.

s Bits 0 to 2: Bit counter (BC0–BC2)

These bits decide the number of bits for the next 1-byte data to be transmitted. An interrupt

request signal occurs immediately after the number of bits specified with these bits are transmitted.

When a START condition is received, these bits become “0002” and the address data is always

transmitted and received in 8 bits.

s Bit 3: I2C-BUS interface use enable bit (ESO)

This bit enables usage of the multi-master I2C-BUS interface. When this bit is set to “0,” the use

disable status is provided, so the SDA and the SCL become high-impedance. When the bit is set

to “1,” use of the interface is enabled.

When ESO = “0,” the following is performed.

• PIN = “1,” BB = “0” and AL = “0” are set (they are bits of the I2C status register at address

00F816).

• Writing data to the I2C data shift register (address 00D716) is disabled.

s Bit 4: Data format selection bit (ALS)

This bit decides whether or not to recognize slave addresses. When this bit is set to “0,” the

addressing format is selected, so that address data is recognized. When a match is found between

a slave address and address data as a result of comparison or when a general call (refer to “(5)

I2C Status Register,” bit 1) is received, transmission processing can be performed. When this bit

is set to “1,” the free data format is selected, so that slave addresses are not recognized.

s Bit 5: Addressing format selection bit (10BIT SAD)

This bit selects a slave address specification format. When this bit is set to “0,” the 7-bit addressing

format is selected. In this case, only the high-order 7 bits (slave address) of the I2C address

addressing format is selected, all the bits of the I2C address register are compared with address

data.

s Bit 6 and 7: Connection control bits between I2C-BUS interface and ports (BSEL0, BSEL1)

This bits controls the connection between SCL and ports or SDA and ports. When using the ports

as multi-master I2C-BUS interface, set the corresponding bits of port P1 direction register to “1”

(output mode).

Figure 2.8.5 shows the connection port control by BSEL0 and BSEL1, Figure 2.8.6 shows the I2C

control register.

Fig. 2.8.5 Connection port control by BSEL0 and BSEL1

“0”

“1” BSEL0

SCL1/P11

SCL2/P12

“0”

“1” BSEL1

“0”

“1” BSEL0

SDA1/P13

SDA2/P14

“0”

“1” BSEL1

Multi-master

I2C-BUS

interface

SCL

SDA

FUNCTIONAL DESCRIPTION

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