BU21025GUL Datasheet, PDF (7/19 Pages) Rohm – 4-wire Resistive Touch Screen Controller

BU21025GUL
Datasheet
Write Protocol
An command write is started in BU21025GUL when the master sends the start condition, the slave address of
BU21025GUL, and zero in bit 0( 8^th bit) for writing, as shown in Table 1. If the slave address is matched with its own,
BU21025GUL issues an acknowledge to the master. When the master receives the acknowledge from BU21025GUL, the
master send the command byte. When BU21025GUL received next 8 bits, it issues another acknowledge to the master.
After the acknowledge is received by the master, the master sends the stop or repeated start condition for ending write.
Figure 1. Write Protocol
If a receiving command in BU21025GUL is not the software reset or setup, BU21025GUL starts driving screen voltage
when C0 is latched by rising edge of SCL. Next, if the received type of operation code is measurement, BU21025GUL starts
acquisition in A/D converter when next falling edge of SCL. BU21025GUL stops acquisition and starts A/D conversion when
BU21025GUL receive the stop or repeated start condition.
When BU21025GUL receives a command other than software reset during the A/D conversion, the command is ignored.
And if the command is ignored, BU21025GUL doesn’t return an acknowledge at the ACK timing behind the command byte.
(18^th timing in Figure. 1)
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7.AUG.2012 Rev.002