TCM4400EPET datasheet(23/64 Pages) TI

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TCM4400E

GSM/DCS BASEBAND AND VOICE A/D

AND D/A RF INTERFACE CIRCUIT

SLWS082A – JULY 1999 – REVISED MARCH 2000

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PARAMETER MEASUREMENT INFORMATION

DSP serial port timing considerations

Figure 4 shows the timing diagram for DSP serial port operation.

Six pins are used for the serial port interface; see Figure 14. The terminal BCLKR is an I/O port for the serial

clock used to control the reception of the data BDR. At reset BCLKR is configured as an output and the clock

frequency is set to MCLK/3 (4.333 MHz with MCLK = 13 MHz); the clock signal is running permanently. The port

BCLKR can be reconfigured as an input by programming an internal register. In this case BCLKR is provided

by the DSP and can run in burst mode to reduce power consumption. The receive frame synchronization (BFSR)

identifies the beginning of a data packet transfer on port BDR.

The transmitted serial data (BDX) is the serial data input; the transmit frame synchronization (BFSX) is used

to initiate the transmission of data. The transmit clock (BCLKX) is provided by the GSM baseband and voice

A/D and D/A converters with a frequency of MCLK. The downlink data bus (BFSX, BCLKX, BDX) can be driven

to VSS or placed in high-impedance when no data is to be transferred to the DSP. The bit BCLKDIR of the

Similar to the voice serial interface, an extra clock cycle must be generated, since the last 16-bit word received

on the DSP serial interface is latched on the next two falling BCLKR edges, following the least significant bit

(LSB). As for the voice serial interface, one extra clock period is generated on the BCLKX before the first

synchronization BFSX of downlink data sequence.

BCLKX

tsu12

th13

tsu13

th14

BFSX

BDX

A15

A14

A13

A12

MSB

LSB

a. Burst-Mode Serial-Port Transmit Operation

tsu14

th14

tsu15

th15

BDR

A15

A14

A13

A12

MSB

LSB

b. Burst-Mode Serial-Port Receive Operation

B15

B14

B13

BCLKR

BFSR

Figure 4. DSP Serial Port Timings

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