TCM8000

CELLULAR TELEPHONE AUDIO PROCESSOR

SCTS041A – D4086, AUGUST 1992 – REVISED APRIL 1993

POST OFFICE BOX 655303

6

detailed description – miscellaneous

crystal oscillator

A low-power crystal oscillator is provided to generate the master clock signal for the switched-capacitor filters.

Sampling frequencies and internal divide ratios have been selected to allow a low cost 3.58-MHz crystal to be

used. No external components except the crystal are required.

DAC

can be used to set limit levels by controlling TXLIM or RXLIM. Its output is unbuffered and should only be used

to drive high-impedance loads.

standby mode

The standby mode disables all signal paths with the exception of the receive data path. In the standby mode,

current consumption is reduced to less than 4 mA.

digital interface

The TCM8000 is configured using a three-wire digital interface. Eight-bit words, comprised of four address and

four data bits, are applied in serial to DATA and clocked into the device on the rising edge of DCLK. The data

is transferred to internal registers by pulsing the LOAD signal high (see Figure 1). All internal registers are reset

low on power up.

DCLK

DATA

LOAD

AD3

AD2

AD1

AD0

D3

D2

D1

D0

Figure 1. Serial Interface Timing Diagram