I'm attempting to write some code to interface with a DS1620. I decided
to do this the hard way, from scratch, on my own. I figured I might as
well dive right in and muck about with everything and see if I can
figure it out.

After dissecting the timing diagrams for the DS1620, I wrote down the
flow of how things are going to occur in the program to communicate with
the temperature sensor chip, what to send, how, etc. Then I started
converting that into assembly.

My main concern, right now, is if there is a significantly better way of
what I am doing. The way I scribbled it down, I'm taking the command
that needs to be sent to the chip and testing the LSB. If the LSB is 0,
I set the pin DQ (Data line) to low, toggle the clock, then go on to the
next bit by rotating right. If a 1, I set DQ high, etc. Rinse, lather,
repeat until no bits need to be sent.

In my mind, this looked like an 'if 0 then send 0 else send 1' to me,
but I couldn't figure out a good way of converting this to assembly. I
ended up using a 'bit test, skip if set/clear' and a 'bit set/clear'
after the appropriate one. It seems so inelegant ...

SendCmd BCF     PORTA,1         ; Bring CLK low
        BTFSC   ReadCmd,0       ; If bit 0 is set, write a 1 to the
        BSF     PORTA,0         ; DQ line
        BTFSS   ReadCmd,0       ; If bit 0 is clear, write a 0 to the
        BCF     PORTA,0         ; DQ line
        BSF     PORTA,1         ; Bring CLK high to tell temp. sensor
                                ; to read the next bit
        DECFSZ  BitCount,1      ; Decrement count of bits left to send
        GOTO    SendCmd         ; If more bits need to be sent ...

Oh, um, sorry for writing so much. O.O Thanks for your help, as well!
Sabachka

--
sabachka@oddmagic.net

"Will there be signs?"
"Yea, the heavens shall open and the NP-complete solution given
forth. ATT executives shall give birth to two-headed operating
systems, and copyrights shall be expunged. The voice of the GNU
shall be heard, but the faithless will be without transceivers."
"There will be signs."

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