# I/O port irregularity? 68HC11

B

#### bruce varley

Jan 1, 1970
0
Hello,

This is probably becoming a legacy topic. I hope there's someone out there
who can assist.

According to the 68HC11 reference manual, Port A PA3-6 can be general
purpose outputs, or driven by timer output compare functions. If one
disables the latter then it should simply be a matter of writing to the PA
register, $1000 to set the pin voltage. I find that that works fine for PA4-6, but despite many attempts I can't set PA3. All the 'obvious' things have been tried. I've reread chapters 7 and 10 in the r.m., and AFAICT the registers are set correctly for gen purpose I/O - OC1M =TCTL1 = CFORC = 0. The pinout diagrams for E2 and E9 chip variants (I use E2) reference an input compare function for the PA3 pin. There's no reference to that elsewhere, it could be the problem but I don't know how to solve it if it is. I need to use this pin as an output. Can anyone assist? TIA T #### timmmmayyy! Jan 1, 1970 0 I`m using the pic877 as an example here but believe you have the same problem. Pin Ra4 on the pic is a pull down only output. Found this out after making 24 boards. Use a pull up resistor. Thanks Good luck R #### Rich Grise Jan 1, 1970 0 Hello, This is probably becoming a legacy topic. I hope there's someone out there who can assist. According to the 68HC11 reference manual, Port A PA3-6 can be general purpose outputs, or driven by timer output compare functions. If one disables the latter then it should simply be a matter of writing to the PA register,$1000 to set the pin voltage.

I find that that works fine for PA4-6, but despite many attempts I can't set
PA3.

All the 'obvious' things have been tried. I've reread chapters 7 and 10 in
the r.m., and AFAICT the registers are set correctly for gen purpose I/O -
OC1M =TCTL1 = CFORC = 0. The pinout diagrams for E2 and E9 chip variants (I
use E2) reference an input compare function for the PA3 pin. There's no
reference to that elsewhere, it could be the problem but I don't know how to
solve it if it is.

I need to use this pin as an output. Can anyone assist? TIA

RTFM:
http://www.freescale.com/files/microcontrollers/doc/data_sheet/M68HC11E.pdf
page 110: DDRA3

Cheers!
Rich

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