PCM4108PAPR datasheet(26/39 Pages) TI

26 / 39 page

PCM4108

SBAS354 − JUNE 2005

www.ti.com

SERIAL PERIPHERAL INTERFACE (SPI) PORT

OPERATION

The SPI port is a five-wire synchronous serial interface that

is used to access the on-chip control registers when the

PCM4108 is configured for Software mode operation. The

CDIN input (pin 31) is the serial data input for the port, while

CDOUT (pin 32) is used for reading back control register

contents in a serial fashion. The CSA (pin 28) and CSB (pin

29) inputs function as the chip selects for register Banks

A and B, respectively. The CCLK input (pin 30) functions

as the serial data clock, used to clock data in and out of the

port. Data is clocked into the port on the rising edge of

CCLK, while data is clocked out of the port on the falling

edge of CCLK.

There are three modes of operation supported for the SPI

port: Single Register, Continuous, and Auto-Increment.

The Single Register and Continuous modes are similar to

one another. In Continuous mode, instead of bringing the

chip select input high after writing or reading a single

byte is issued with a new address for the next write or read

operation. Continuous mode allows multiple, sequential or

nonsequential register addresses to be read or written in

succession, as shown in Figure 16.

Auto-Increment mode is designed for writing or reading

multiple sequential register addresses. After the first

automatically incremented by 1, so the next write or read

operation is performed without issuing another control

byte, as shown in Figure 17.

Control Byte (or Byte 0)

The control byte, or byte ‘0’, is the first byte written to the

PCM4108 SPI port when performing a write or read

operation. The control byte includes bits that define the

operation

performed

(read

write),

the

auto-increment mode status, and the control register

address.

The Read/Write bit, R/W, is set to ‘0’ to indicate a register

write operation, or set to 1 for a register read operation.

The Increment bit, INC, enables or disables the

Auto-Increment mode of operation. When this bit is set to

a ‘0’, auto-increment operation is disabled, and the

operation

performed

either

Single

Continuous.

Setting

the

INC

bit

‘1’

enables

Auto-Increment operation.

A two-bit key code, 10B, follows the INC bit and must be

present in order for any operation to take place on the

control port. Any other combination for these bits will result

in the port ignoring the write or read request.

The four-bit address field, A[3:0], is used to specify the

control register address for the read or write operation, or

the starting address for an Auto-Increment write or read

operation.

CSA

CSB

CDIN

CCLK

Keep CSA and/or CSB low for writing or reading multiple registers in Continuous mode

byte 0

byte 1

byte 0

byte 1

byte N

Auto−Increment Control: Set to 0 for Single Register or Continuous Operation

Read/WriteControl: 0 = Write

1 = Read

Control Byte

CDOUT

High Impedance

byte 1

High Impedance

byte 2

byte N

R/W INC

MSB

LSB

Control Byte Definition (Byte 0)

Figure 16. Single Register and Continuous Write or Read Operation

PCM4108PAPR Datasheet(PDF) 26 Page - Texas Instruments

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