Reading a port

Curtis Brooks

Is there a way to read the current state of an entire port?

For instance, if I have some of the port pins high and some low is there a way to read the state of the port into a variable?

Worapoht

try this procedure:
first check port direction from DIRx (x is port name) and seperated case by
if DIRx = 0, current port is defined as input, check input on INx
if DIRx = 1, current port is defined as ouput, check current output state on OUTx

Curtis Brooks

Okay. So could I do something like this:

setportA VAR OUTA
setportB VAR OUTB

setportA = %1111
setportB = %0000

DEBUG setportA
DEBUG setportB
END

Will debug display the current state of the port this way?

Jon Williams

Yes. INS reads all 16 pins; INL reads pins 0-7, INH reads pins 8 - 15; INA is pins 0 - 3; INB is pins 4 - 7; INC is pins 8 - 11; and IND is pins 12 - 15.

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Jon Williams
Applications Engineer, Parallax
Dallas Office

Worapoht

Yes, you can do. just a little changed on debug command

setportA VAR OUTA
setportB VAR OUTB

setportA = %1111
setportB = %0000

' I'd added modifier to show on debug term as two lines 4 binary digits format.
DEBUG BIN4 setportA,CR
DEBUG BIN4 setportB
END

allanlane5

I thought you wanted to READ the state of a port. All the solutions presented so far WRITE out a port.

To READ the state of a port, you have to set the port as an INPUT (PIC and BS2 gotcha).

So:
ReadPortA VAR INA ' Create alias
ReadPortB VAR INB ' Create another alias
MyVal VAR BYTE

INPUT PORTA ' Set PortA bits as INPUT. See also the 'DIRA' variable.
MAIN:
MyVal = ReadPortA
DEBUG BIN8 MyVal, CR
PAUSE (100) ' 100 mSec, so we're not FLOODED with data...
GOTO MAIN