hd66740 Renesas Electronics Corporation., hd66740 Datasheet - Page 39

• Manufacturer Part Number: hd66740
• Description: 112 X 80-dot Graphics Lcd Controller/driver - Hitachi Semiconductor
• Manufacturer: Renesas Electronics Corporation.

Serial Data Transfer (I2C bus interface)
Setting the IM2=Vcc and IM1=GND level allows I2C bus interface, using the serial data line (SDA) and
serial transfer clock line (SCL). For the I2C bus interface, the IM0/ID pin function uses an ID pin.
The HD66740W is initiated serial data transfer by transferring the first byte when a high SCL level at the
falling edge of the SDA input is sampled; it ends serial data transfer when a high SCL level at the rising
edge of the SDA input is sampled.
Table 16-a illustrates the start byte of I2C bus interface data and Figure 16-a and 16-b show the I2C bus
interface timing sequence.
The HD66740W is selected when the higher 6-bit slave address in the first byte transferred from the
master device match the 6-bits device identification code assigned to the HD66740W. The HD66740W,
when selected, receive the subsequent data string. The lower 1-bit of the device identification code can be
determined by the ID pin; select an appropriate code that is not assigned to any other slave device. The
upper five bits are fixed to 01110. One slave address is assigned to a single HD66740W.
The ninth bit of the first byte is a receive-data acknowledge bit (ACK). When the received slave address
matches the device ID code, HD66740W pulls down the ACK bit to a low level. Therefore, the ACK
output buffer is an open-drain structure, only allowing low-level output. However, the ACK bit is
undermined immediately after power-on; make sure to initialize the LSI using the RESET* input.
After identifying the address in the first byte, the HD66740W receives the subsequent data as an
HD66740W instruction or as RAM data. Having received 8-bit data normally, HD66740W pulls down
the ninth bit (ACK) to a low level. The instruction or RAM data is 8-bits data format.
Two bytes of RAM read data after the start byte are invalid. The HD66740W start to read correct RAM
data from third byte.
Table 16-a Start Byte Format
Transfer Bit
Start byte format
Note: ID bit is selected by the IM0/ID pin.
Table 16-b RS and R/W bit function
RS
0
0
1
1
R/W
0
1
0
1
Function
Writes instruction
-
Writes RAM data
Reads RAM data
S
Transfer start
1
0
2
1
39
Device ID code
3
1
4
1
5
0
6
ID
7
HD66740
RS
8
R/W
9
ACK