On Sat, 2006-12-30 at 16:43 -0500, Carl Moreschi wrote:
> The baud rate for the Orion is fixed at 57600 baud. And a DOS program does
> have a limit of 9600 baud so I would say you cannot do it with NA. But CT
> looks just like NA and is now free and does have a windows version that
> works with the Orion.
>
> Carl Moreschi N4PY
> 121 Little Bell Drive
> Bell Mountain
> Hays, NC 28635
DOS interrupts only support up to 9600 baud, but the hardware supports
faster. The clock divisor is 12 for 9600 baud, so 57600 needs a divisor
of 2. Looking at an old DOS programming book you have to set DLAB (bit 7
in the Line Control Register, base + 3) high then you write the divisor
to base + 0 and base + 1, for the LSB and the USB of the divisor. Base +
0 is the incoming data register when DLAB = 0, and Base + 1 is the send
data register.
So its clear that my DOS programs never exceed 112.2 Kb where the
divisor is 1. Though the later chips may use a higher clock speed,
because Linux here shows speeds up to 460.8 Kb. So it behooves the
programmer to use dos interrupts to set the serial port to 9600, then go
read the divisor registers and adjust from there with 57.6 K being 6
times faster or 1/6th the divisor. Reading takes setting DLAB = 1 also.
73, Jerry, K0CQ
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