MAC7200 datasheet(927/976 Pages) FREESCALE

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Initialization/Application Information

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

849

be rather inefficient, and can not easily be programmed into a DMA. The next example illustrates how to

use the Pin Data Register (PINDATAxx) to overcome these two disadvantages.

NOTE

The PINDATAxx register is simply a "mirror" of the corresponding bit in the

PORTDATA register. Therefore writes to the PORTDATA register will

change the read value of a PINDATAxx register, and vice-versa.

Example 34-4. Disable the IIC and use its two pins as general purpose inputs

In File registers.h:

#define PIM_BASE_ADDRESS

0xFC0E8000/* Example only ! */

/* Following example assumes ’char’ is 8-bits and ’short’ is 16-bits */

volatile unsigned short *CONFIG_B0 = (volatile unsigned short *) (PIM_BASE_ADDRESS+0x0040);

volatile unsigned short *CONFIG_B1 = (volatile unsigned short *) (PIM_BASE_ADDRESS+0x0042);

volatile unsigned char *PINDATA_B0 = (volatile unsigned char *) (PIM_BASE_ADDRESS+0x0064);

volatile unsigned char *PINDATA_B1 = (volatile unsigned char *) (PIM_BASE_ADDRESS+0x0065);

In File main.c:

#include "registers.h"

/* Initialize Port B */

*CONFIG_B0 = 0x0000;/* GPIO Mode: Input, No interrupt */

*CONFIG_B1 = 0x0000;/* GPIO Mode: Input, No interrupt */

/* Sample Ports B0 & B1 */

unsigned char value_B0;

unsigned char value_B1;

value_B0 = *PINDATA_B0;/* Equivalent to (*PORTDATA_B & 0xF001) >> 0 */

value_B1 = *PINDATA_B1;/* Equivalent to (*PORTDATA_B & 0x0002) >> 1 */

Like the PORTDATA register, writes to the PINDATA registers for input pins have no effect (other than

to set the corresponding bit in the PORTDATA register). Therefore, it is possible to use a DMA to drive

multiple pins, even though the pins may not be contiguous (i.e.-Pins B0-B3 and B5-B8). Conversely, reads

from the PINDATA registers for output pins will simply return the value of the corresponding bit in the

PORTDATA register. The next section illustrates how to use a DMA with trigger capability to implement

periodic protocols (such as PWM) on the GPIO ports.

34.8.2.2.3

Using a DMA

As seen in the previous section, it is relatively easy to drive or sample multiple pins without the need for

mask or shift operations, using the PINDATAxx registers. This allows the use of a DMA to copy entire

tables of data from/to several pins at a time. In addition to standard DMA operations, the Port Integration

Module also supports the use of DMA triggers to perform periodic copies of data, allowing you to easily

implement protocols such as Pulse Width Modulation. For more details on how to setup and configure

DMA triggers, please refer to the section covering the DMA Channel Mux. In general, the procedure is as

follows:

1. Configure the Port Integration Module

2. Configure the DMA to copy tables of data from memory to the Port Integration Module

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