CS3318 Datasheet, PDF (27/44 Pages) Cirrus Logic – 8-Channel Analog Volume Control

CS3318
5.9 I²C/SPI Serial Control Formats
The control port is used to access the internal registers of the CS3318. The control port has 2 modes: SPI
and I²C, with the CS3318 acting as a slave device. SPI Mode is selected if there is a high-to-low transition
on the CS pin after the RESET pin has been brought high. I²C Mode is selected by connecting the CS pin
to VD or DGND.
5.9.1
I²C Mode
In I²C Mode, SDA is a bidirectional data line. Data is clocked into and out of the CS3318 by the clock,
SCL. The AD0 pin sets the least significant bit of the default chip address and must be connected to VD
or DGND. The AD0 pin is read upon the release of the RESET signal (a low-to-high transition), and its
value (‘0’ when connected to DGND, ‘1’ when connected to VD) is reflected in the LSB of the chip address
in the Individual, Group 1, and Group 2 Chip Address registers. Table 4 shows the default chip addresses
in I²C Mode.
AD0 Connection
DGND
VD
Default Chip Address
1000000b
1000001b
Table 4. I²C Mode Default Chip Address
The signal timings for a read and write cycle are shown in Figure 12 and Figure 13. A Start condition is
defined as a falling transition of SDA while the clock is high. A Stop condition is a rising transition while
the clock is high. All other transitions of SDA occur while the clock is low.
The first byte sent to the CS3318 after a Start condition consists of a 7-bit chip address field and a R/W
bit (high for a read, low for a write). To communicate with a CS3318, the chip address field should match
either the Individual, Group 1, or Group 2 device address as set by their respective control port registers.
The eighth bit of the address is the R/W bit. If the read/write bit is set high (indicating a read operation)
and the preceding 7 bits do not match its Individual address, the CS3318 will ignore all traffic on the I²C
bus until a Stop and Start condition occurs.
If the operation is a write, the next byte is the Memory Address Pointer (MAP) which selects the register
to be read or written. If the operation is a read, the contents of the register pointed to by the MAP will be
output.
There is a MAP auto-increment capability, enabled by the INCR bit (the MSB of the MAP byte). If INCR
is ‘0’, the MAP will stay constant for successive read or writes. If INCR is ‘1’, the MAP will automatically
increment after each byte is written, allowing block writes of successive registers. Each byte is separated
by an acknowledge (ACK) bit. The ACK bit is output from the CS3318 after each input byte is read and is
input to the CS3318 from the microcontroller after each transmitted byte.
SCL
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 24 25 26 27 28
CHIP ADDRESS (WRITE)
MAP BYTE
DATA
DATA +1
SDA
MSB
START
Chip Address
LSB 0
INCR 6 5 4 3 2 1 0
76
ACK
ACK
10
76
ACK
10
Figure 12. Control Port Timing, I²C Write
DATA +n
76 10
ACK
STOP
DS693F1
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