TMS320LC2401AVFS datasheet(57/134 Pages) TI

57 / 134 page

TMS320LF2407A,TMS320LF2406A,TMS320LF2403A,TMS320LF2402A

TMS320LC2406A,TMS320LC2404A,TMS320LC2403A,TMS320LC2402A

DSP CONTROLLERS

SPRS145K − JULY 2000 − REVISED AUGUST 2005

POST OFFICE BOX 1443

• HOUSTON, TEXAS 77251−1443

SPI slave mode operation in LF2403A

The LF2403A device does not have the SPISTE/IOPC5 pin. (This function is available as an internal signal only.)

The following must be done to put the LF2403A SPI in slave mode:

1. Configure SPISTE/IOPC5 signal for GPIO mode by clearing the MCRB.5 bit.

2. Configure SPISTE/IOPC5 signal as an output (by writing a 1 to bit 13 of PCDATDIR) and drive it low (by

writing a 0 to bit 5 of PCDATDIR). Note that SPISTE/IOPC5 should not be driven low until after the SPI is

configured and taken out of reset.

NOTE: The slave SPISTE/IOPC5 signal must not be driven low until after the master and slave SPI modules

are configured and taken out of reset. The initialization sequence is as follows:

a. The master SPI is configured first and taken out of reset. This ensures that the master SPICLK is

initialized to its appropriate level (high or low, depending on the polarity bit) first, before the slave SPI

starts accepting clock pulses.

b. The slave SPI is configured and taken out of reset.

c. The GPIO/SPI pins of the slave is then configured for SPI operation and the SPISTE/IOPC5 signal is

driven low. This is done after ensuring the correct level of the master SPICLK signal. One method of

doing this would be to read the level of the SPICLK pin through the PCDATDIR register and then

deciding on the appropriate course of action.

d. SPI transmission may commence now. Transmission of data should not be attempted until both master

and slave are configured and the slave SPISTE/IOPC5 signal is driven low.

PLL-based clock module

The 240xA has an on-chip, PLL-based clock module. This module provides all the necessary clocking signals

for the device, as well as control for low-power mode entry. The PLL has a 3-bit ratio control to select different

CPU clock rates. See Figure 16 for the PLL Clock Module Block Diagram, Table 9 for clock rates, and Table 10

for the loop filter component values.

The PLL-based clock module provides two modes of operation:

D Crystal-operation

This mode allows the use of an external crystal/resonator to provide the time base to the device.

D External clock source operation

This mode allows the internal oscillator to be bypassed. The device clocks are generated from an external

clock source input on the XTAL1/CLKIN pin. In this case, an external oscillator clock is connected to the

XTAL1/CLKIN pin.

TMS320LC2401AVFS датащи(PDF) 57 Page - Texas Instruments