SX8652ICSTRT Semtech, SX8652ICSTRT Datasheet - Page 18

• Manufacturer Part Number: SX8652ICSTRT
• Description: 4/5-wire Resistive Touch Screen Controller (SPI)
• Manufacturer: Semtech

6.1.1. SPI Read/Write Registers
The host can write to and read from registers of the SX8652 by the write and read commands as defined in Table 8.
With the WRITE command, the host can write a single or multiple registers in the SX8652 register. This command is
generated by setting the CMD(7:5) bits to write command (000). The register address is latched after the address is
received and used for the first write.
With the READ command the host can read a single or multiple registers in the SX8652 register file. The frame starts by
issuing a write command indicating the address of the first register to be read and the data are put on the DOUT line.
6.1.2. SPI Reading Channel Data
The data read process is the same as the register read process, but with a different command. Channel data are stored in
a FIFO stack with the order: First: X,Y, Z1, Z2, Last: AUX. It is not possible to read two times the same coordinate. When
the channel data buffer gets empty, the data will carry an invalid data as explained in the channel data format.
For example, if the value 0xC0 is set in RegChanMsk (X and Y conversion), the first READCHAN command will read X
value, the second will read Y value and the third one will get invalid data.
The channel data D(11:0) is of unsigned format and corresponds to a value between 0 and 4095.
This is send on 2 bytes of 8 bits. A mask with the value 0x0FFF (4095) must be done to get correct values.
6.1.3. Multiple Read/Write
The SPI protocol is designed to be able to do multiple read/write during a transaction. During one single operation, as long
as NCS stay asserted, the register address is automatically increased to allow sequential read/write (or sequential retrieval
of data). Between each different operation though (READ/WRITE/READCHAN), the communication should be restarted.
This is described in Figure 20.
Revision V1.6/July 2010
©2010 Semtech Corp.
ADVANCED COMMUNICATIONS & SENSING
W/R command name
W/R command name
Read/Write Registers
Read Channels Data
Host Commands
READCHAN
WRITE(RA)
READ(RA)
7
7
0
0
0
6
0
1
6
0
5
5
0
0
1
Table 9.
Table 8.
4
4
x
CR(7:0)
CR(7:0)
15kV ESD Low Power 4-Wire / 5-Wire Resistive
Read Channels Data
Page 18
3
3
x
W/R commands
RA(4:0)
RA(4:0)
Touchscreen Controller with SPI Interface
2
2
x
1
1
x
0
0
x
Write register (see Table 12 for RA)
Read register (see Table 12 for RA)
Read Channel Data
Function
Function
www.semtech.com
DATASHEET
SX8652