
32
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
with ON-SCREEN DISPLAY CONTROLLER
M37225M6/M8/MA/MC–XXXSP
M37225ECSP
MITSUBISHI MICROCOMPUTERS
Rev. 1.0
8.6.1 I2C Data Shift Register
The I2C data shift register (S0 : address 00D716) is an 8-bit shift
register to store receive data and write transmit data.
When transmit data is written into this register, it is transferred to the
outside from bit 7 in synchronization with the SCL clock, and each
time one-bit data is output, the data of this register are shifted one bit
to the left. When data is received, it is input to this register from bit 0
in synchronization with the SCL clock, and each time one-bit data is
input, the data of this register are shifted one bit to the left.
The I2C data shift register is in a write enable status only when the
ESO bit of the I2C control register (address 00DA16) is “1.” The bit
counter is reset by a write instruction to the I2C data shift register.
When both the ESO bit and the MST bit of the I2C status register
(address 00D916) are “1,” the SCL is output by a write instruction to
the I2C data shift register. Reading data from the I2C data shift regis-
ter is always enabled regardless of the ESO bit value.
Note: To write data into the I2C data shift register after setting the MST bit to
“0” (slave mode), keep an interval of 8 machine cycles or more.
Fig. 8.6.2 Data Shift Register
b7 b6 b5 b4 b3 b2 b1 b0
0
Read/write bit
(RBW)
1
to
7
Slave address
(SAD0 to SAD6)
<Only in 10-bit addressing (in slave) mode>
The last significant bit of address data is
compared.
0: Wait the first byte of slave address after
START condition
(read state)
1: Wait the first byte of slave address after
RESTART condition
(write state)
0
<In both modes>
The address data is compared.
I2C Address Register
I2C address register (S0D) [Address 00D816]
B
Name
Functions
After reset R W
R—
R W