CS4812

DS291PP3

31

Serial Control Port

SCPM/S - Serial Control Port Master/Slave Select

Input: This pin configures the serial control port as a master if tied to VD or a slave if tied to DGND.

SCL/CCLK - Serial Control Port Clock

clocks control port data into CDIN and out of CDOUT. When the serial control port is configured as a

master, SCL/CCLK is an output and is generated internally. When the serial control port is configured as

a slave, SCL/CCLK is an input and may operate asynchronously to the master clock.

bits of the 7-bit address must be 00100. In SPI mode, CS is the chip select pin. When the serial control

port is defined as a master in SPI mode, CS is an output. When the serial control port is defined as a

slave in SPI mode, CS is an input.

the 7-bit address must be 00100. In SPI mode, CDIN is the serial control port data input and is clocked

in on the rising edge of CCLK.

control port data output and is clocked out on the falling edge of CCLK.

REQ - DSP Output Request

Output: This pin is used when the serial control port is configured for slave mode operation. This pin is

asserted when the DSP has written a byte to a register in the control port. When this register is read by

the master device, REQ is de-asserted.

Clock and Crystal

XTI, XTO - Crystal Oscillator Connections (Master Clock)

Input, Output: These pins provide connections for an external parallel resonant quartz crystal.

Alternately, an external clock source may be applied to XTI. The clock frequency must be 256xFs.

CLKOUT - Clock Output

Output: This pin provides a clock output which can be used to synchronize external components.

Available output frequencies 1xFs, 128xFs and 256xFs are selectable via a control port register. The

default frequency is 256xFs. It is recommended to externally buffer this signal with a CMOS gate as

shown in Figure 5.

Miscellaneous

PIO0:3 - General Purpose Inputs/Outputs

Bidirectional: These pins are general-purpose digital I/O pins. The Default state is input. The

functionality of these pins after boot-up is determined by the application firmware code loaded into the

device during the boot-up process.

RST - Reset

Input: This pin causes the device to enter a low power mode and forces all control port and i/o registers

to be reset to their default values. The control port can not be accessed when reset is low.