TMS320C242FN datasheet(13/66 Pages) TI

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TMS320C242

DSP CONTROLLER

SPRS063B – DECEMBER 1997 – REVISED DECEMBER 1999

POST OFFICE BOX 1443

• HOUSTON, TEXAS 77251–1443

digital I/O and shared pin functions

The ’C242 has a total of 26 general-purpose, bidirectional, digital I/O (GPIO) pins –most of which are shared

between primary functions and I/O. Twenty (20) I/O pins of the ’C242 are shared with other functions. The digital

I/O ports module provides a flexible method for controlling both dedicated I/O and shared pin functions. All I/O

and shared pin functions are controlled using eight 16-bit registers. These registers are divided into two types:

D Output Control Registers — used to control the multiplexer selection that chooses between the primary

function of a pin or the general-purpose I/O function.

D Data and Control Registers — used to control the data and data direction of bidirectional I/O pins.

description of shared I/O pins

The control structure for shared I/O pins is shown in Figure 3, where each pin has three bits that define its

operation:

D Mux control bit — this bit selects between the primary function (1) and I/O function (0) of the pin.

D I/O direction bit — if the I/O function is selected for the pin (mux control bit is set to 0), this bit determines

whether the pin is an input (0) or an output (1).

D I/O data bit — if the I/O function is selected for the pin (mux control bit is set to 0) and the direction selected

is an input, data is read from this bit; if the direction selected is an output, data is written to this bit.

The mux control bit, I/O direction bit, and I/O data bit are in the I/O control registers.

Primary

Function

(Read/Write)

IOP Data Bit

Out

0 = Input

1 = Output

MUX Control Bit

0 = I/O Function

1 = Primary Function

IOP DIR Bit

Primary

Function

or I/O Pin

When the MUX control bit = 1, the primary

function is selected in all cases except

for the following pins:

1. XF/IOPC0 (0 = Primary Function)

2. BIO/IOPC1 (0 = Primary Function)

3. CLKOUT/IOPD0 (0 = Primary Function)

Note:

Figure 3. Shared Pin Configuration

A summary of shared pin configurations and associated bits is shown in Table 3.

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