How to use Port C and D as general purpose I/O

[adonisk]

Hi, I'v very new on freescale, now I'm using S12X chip and I want use port c and d to control some LED.

but port C and D in S12X is using for EBI in default.

It's said: When not used with the alternative function, these pins can be used as general purpose I/O.

My question is: how to disable EBI and use port C D as general I/O?

Please show me code if possible.

Thank you for you reply.

[adonisk]

I'm using XEP100 by the way.

It's said like this on Reference Manual:

2.4.3.3 Port C, D

Port C pins PC[7:0] and Port D pins PD[7:0] can be used for either general-purpose I/O with the external

bus interface. In this case Port C and Port D are associated with the external data bus inputs/outputs

DATA15-DATA8 and DATA7-DATA0, respectively.

These pins are configured for reduced input threshold in certain operating modes (refer to S12X_EBI

section).

But I never found any information how to config it as general-purpose I/O within chapter S12X_EBI.

[RadekS · Accepted solution]

Hi Adonis,

External bus is 2^nd Functionality (See Table 1-9. Pin-Out Summary).

When pins are not used with the any of alternative functions, these pins can be used as general purpose I/O.

So, you can use Port C/D as GPIO until you enable XEBI module. XEBI module could be used (is enabled) only in expended or emulated modes.

So, if you will use your MCU in normal or special single chip mode (MODA=MODB=0), you can use Port C/D only as GPIO.

For direction of port C/D, please use DDRC/DDRD registers. You can read/write value trough PORTC/PORTD registers.

Unfortunately ports C and D do not provide such high flexibility as other ports. You can just enable pull-ups (pull-down is not possible) and these pull-ups could be enabled only for whole port (we cannot choose which pins will have pull-ups). For more details, please check PUCR register.

I hope it helps you.

Have a great day,
RadekS

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[adonisk]

You are correct!

Thank you RadekS, you did great help, I do appreciate for you.