sending serial data, bit by bit, to a specific pin in pasm

Jeffrey Kane

Yes, I know this is a beginner question, but my brain locked up

in pasm, I have a long with various bits

test_bit_mask long %10101010_11110001_11110000_11110001

and I want to send this to a specific pin on the prop1 (in pasm), which happens to be what I am using, one bit at a time, shifting right to left

so the output to the pin would go

1,0,1,0,1,0,10,1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,1

say for example my pin that I want to send the data to is pin 15,

:Pin_looper xor outa, pin_15 'toggle pin 15
djnz pin_length, #:Pin_looper 'return to caller pin_length is set to 32, the xor simply toggles the pin

but if I want to send a random set of bits to the pin, I don't know

it would be something like: (in c ish)
array_of_bits long {1,0,1,0,1,0,10,1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,1}

for (int i= 0;i<32;i++)
pin15 = array_of_bits[i]

I'm thinking it has something to do with
test pinMask, ina wc
rcl readbit,#1

any help would be appreciated, if this has already been done a million times, a link would be fine.

thank you

Jeff

Jeffrey Kane

I may have explained this wrong, the output of the above bitmask (1,0,1,0,1,0,1,0,1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,1)

would be on the pin as
High,low,high,low,high,low,high,low,high,high,high,high,low,low,low,low,high,high,high,high,low,low,low,high

currently it looks like this, (since it is xor'ed)

Jeff

Ariba

This can be done with the help of the Carry flag. The shift instructions can shift the bits into the Carry, and there is the MUXC instruction to set specific bits in a register to the state of the Carry. If this register is OUTA, you set port bits.

           or     dira, portbitmask          'set port pin to output
           mov    bitcounter, #32

pin_loop   shl    test_bit_mask, #1   wc      'shift left by 1, shifted out bit goes into Carry Flag
           muxc   outa, portbitmask           'set pin (15 here) to the state of the Carry Flag
           djnz   bitcounter, #pin_loop


test_bit_mask  long   %10101010_11110001_11110000_11110001
portbitmask    long   1<<15                   'bit mask for pin 15

bitcounter     long   0

Andy

Jeffrey Kane

works nicely, thanks

Here is the data:
test_bit_mask long %10000001_01111110_11110001_11001100