TMS320LC2401AVFS datasheet(17/88 Pages) TI

17 / 88 page

TMS320LF2401A, TMS320LC2401A

DSP CONTROLLERS

SPRS161K − MARCH 2001 − REVISED JULY 2007

POST OFFICE BOX 1443

• HOUSTON, TEXAS 77251−1443

constraints while emulating with JTAG port pins and GPIO functions

This section highlights the constraints that are encountered if the emulation/debugging tool attempts to use the

multiplexed JTAG/GPIO pins in their JTAG configuration while the application attempts to use them in the GPIO

configuration at the same time:

Since the emulation/debugging tools need complete control of the JTAG port pins, the GPIO functions that

are multiplexed with the JTAG port pins cannot be used when the JTAG pod is connected to the JTAG

header.

Applications using the JTAG port pins for its GPIO function must provide some isolation mechanism (such

as jumpers) to isolate the external circuitry associated with the GPIO circuits. This will ensure that the GPIO

circuit does not conflict with the signals from the JTAG pod. To reiterate, the circuitry associated with the

GPIO pins must be isolated from the DSP before the JTAG pod is connected to the JTAG header.

It is recommended that the Lx2401A application software does not enable GPIO function for the multiplexed

JTAG/GPIO pins if emulation tools are ever planned to be used concurrently. This will avoid drive conflicts

between JTAG pod signals and GPIO signals—particularly on TCK, TDI and TMS pins. Table 2 shows the

configuration of the multiplexed JTAG/GPIO pins depending on the status of the TRST pin.

Table 2. Configuration of Multiplexed JTAG/GPIO Pins

TRST = 1

TRST = 0

TCK (signal from the JTAG pod)

Can be configured as IOPB1

TDI (signal from the JTAG pod)

Can be configured as OPB5

TMS (signal from the JTAG pod)

Can be configured as XF

TRST pin is internally pulled down. When this pin is left unconnected, it puts the multiplexed JTAG/GPIO

pins in their GPIO configuration. If TRST is driven high, it puts the multiplexed JTAG/GPIO pins in their JTAG

configuration and the device enters emulation mode. All the emulation and flash programming tools use the

JTAG port and will drive this pin high. TRST pin controls the functionality of the multiplexed JTAG/GPIO pins.

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