Greetings:
I have for some days been struggling with achieving consistent and accurate
serial port operation, especially when the Interrupts are being hit at a
high rate. The APNOTE from MICROCHIP does not work most of the time and
never worked properly. However a fine piece of work by Tom McGahee,
PICUART.ASM for the 16C74A should be adaptable to the 16F628.
It was adaptable and works like a charm. I have now tried this with the
following Oscillator configurations. For the 16F628, the Internal 4 MHz,
an external 4 MHz crystal, a 1.8432 MHz crystal and with a high speed
16F628 it ran just fine with a 21.7 MHz crystal.
I will send any and all who ask a copy of this ASM file, which I happen to
call PIC8_4B.ASM, configured to run on a 4 MHz crystal or 4 MHz internal
oscillator by just compiling it with MPASM.
I will decline to express my thoughts about Microchip documentation and
product support. It is suffice to say that my first copy of CPM-80, the
one with both handwritten and typewritten documentation from Gary Kendall
about 1976/7 was of higher quality and vastly more accurate than what I
have received from Microchip for the 16F628.
Larry Kayser
VA3LK
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