BU21029GUL Datasheet, PDF (9/29 Pages) Rohm – 4-wire Resistive Touch Screen Controller

BU21029GUL
Datasheet
●WRITE CYCLE
The host first sends an address byte to the BU21029GUL controller. This address byte is composed of the 7-bit slave byte
on the upper seven bits and the Read/Write bit on the LSB. If the controller receives a valid address byte, it issues an
acknowledgement. The host processor can transmit a command only after receiving the acknowledgement for the address
byte from the controller. The controller then sends back another acknowledgement, allowing the host to continually send
write data or issue a STOP command.
S：START condition
P：STOP condition A：ACK N：NACK
Figure 1. Write Protocol
●READ CYCLE
The READ bit is the LSB of the address byte. When read mode is selected, BU21029GUL sends back the data byte
followed by an acknowledgement to the host. The data sent back is either the conversion result or the register value,
depending on the last command byte received by BU21029GUL. The host needs to resend the conversion command with
setting "CMSK=1" if it has read the register value before reading the conversion result. BU21029GUL sends the next data
byte after it has received an acknowledgement from the host for the previous data byte. Upon receiving the last data byte,
the host finishes read access by issuing a START (or STOP) commands followed by NACK (not acknowledged) command.
S：START condition
P：STOP condition A：ACK N：NACK
Figure 2. Read Protocol
●SCL STRETCH
If the host reads the conversion result while conversion is ongoing, BU21029GUL notifies it through the SCL_STRETCH
function. (*1) SCL_STRECH is released when conversion function is finished.
Figure 3. SCL Stretch Timing
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11.Nov.2013 Rev.002