CS42325
Send start condition.
Send 10011xx0 (chip address & write operation).
Receive acknowledge bit.
Send MAP byte, auto increment off.
Receive acknowledge bit.
Send stop condition, aborting write.
Send start condition.
Send 10011xx1(chip address & read operation).
Receive acknowledge bit.
Receive byte, contents of selected register.
Send acknowledge bit.
Send stop condition.
Setting the auto increment bit in the MAP allows successive reads or writes of consecutive registers. Each
byte is separated by an acknowledge bit.
4.6.3
Software Mode - SPI Control Port
In SPI Mode, data is clocked into the serial control data line, CDIN, by the serial clock, CCLK (see Figure 22
for the clock to data relationship). There are no AD0 or AD1 pins. Pin CS is the chip select signal and is
used to control SPI writes to the registers. When the device detects a high-to-low transition on the AD0/CS
pin after power-up, SPI Mode will be selected. All signals are inputs and data is clocked in on the rising edge
of CCLK.
4.6.3.1 SPI Write
To write to the device, follow the procedure below while adhering to the Software Mode switching speci-
fications in “Switching Characteristics - Software Mode - SPI Format” section on page 25.
1. Bring CS low.
2. The address byte on the CDIN pin must then be 10011110 (R/W = 0).
3. Write to the memory address pointer, MAP. This byte points to the register to be written.
4. Write the desired data to the register pointed to by the MAP.
5. If the INCR bit (see Section 4.6.4.1) is set to 1, repeat the previous step until all the desired registers
are written, then bring CS high.
6. If the INCR bit is set to 0 and further SPI writes to other registers are desired, it is necessary to bring
CS high, and follow the procedure detailed from step 1. If no further writes to other registers are
desired, bring CS high
4.6.3.2 SPI Read
To read from the device, follow the procedure below while adhering to the values specified in “Switching
Characteristics - Software Mode - SPI Format” section on page 25.
1. Bring CS low.
2. The address byte on the CDIN pin must then be 10011111 (R/W = 1).
3. CDOUT pin will then output the data from the register pointed to by the MAP, which is set during the
SPI write operation.
4. If the INCR bit (see Section 4.6.4.1) is set to 1, keep CS low and continue providing clocks on CCLK
to read from multiple consecutive registers. Bring CS high when reading is complete.
42
DS838A2
CIRRUS [ CIRRUS LOGIC ]
