Baud and parity settings in V3.3\C4PMF

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lowrybt1
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Baud and parity settings in V3.3\C4PMF

Post by lowrybt1 »

Two questions:

Other than cutting a trace and adding a jumper to the 505 board, is there a way to poke the printer/modem ports on a C4P to operate at 9600 baud?

Does the C4PMF serial port use the standard 8N1 protocol? If not, is there a way to poke that protocol into effect?

(Okay, that's 3 questions)

Thanks, Tom
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dave
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Re: Baud and parity settings in V3.3\C4PMF

Post by dave »

lowrybt1 wrote: Wed Aug 09, 2017 3:49 am Two questions:

Other than cutting a trace and adding a jumper to the 505 board, is there a way to poke the printer/modem ports on a C4P to operate at 9600 baud?

Does the C4PMF serial port use the standard 8N1 protocol? If not, is there a way to poke that protocol into effect?

(Okay, that's 3 questions)

Thanks, Tom
I would not consider the jumper cut to even be a real mod, as it's the way the board is designed to be used.

That being said, the ACIA has 3 clock divide rates, /1, /16, and /64. These are selected by setting the lowest two bits of the ACIA control work ($FC00 = 64512) to 0, 1, or 2 respectively. The C4P manual even suggests switching between 300 baud and 1200 baud by poking a 1 (1200 baud) or 2 (300 baud) at 64512 ($FC00). If you set the bottom two bits to 0, you get divide by 1, or 19200 baud. It may work fine, but 1x is really intended for synchronous data, and for asynchhronous serial, 1x will not be as inherently robust as a 16x clock.

The next 3 bits indicate the packet type:

0 0 0 -> 7 bit word, even parity, 2 stop bits
0 0 1 -> 7 bit word, odd parity, 2 stop bits
0 1 0 -> 7 bit word, even parity, 1 stop bit
0 1 1 -> 7 bit word, odd parity, 1 stop bit
1 0 1 -> 8 bit word, 2 stop bits
1 0 1 -> 8 bit word, 1 stop bit
1 1 0 -> 8 bit word, even parity, 1 stop bit
1 1 1 -> 8 bit word, odd parity, 1 stop bit

So, 8N1 and 19200 baud would poke 10100 - $14 =20(dec) to $FC00. If you select the jumper for 9600 baud, then you can use a 16x setting, and the 64x setting would 2400 baud (I think.)

Cheers,

Dave
lowrybt1
Posts: 212
Joined: Sun Mar 08, 2015 3:42 pm
Location: New York State

Re: Baud and parity settings in V3.3\C4PMF

Post by lowrybt1 »

Many thanks!!
C8PDF w. 48K, 2x 520 24K RAM boards and Glitchworks 64K board
OSI 567 Telephony board
Spare 8" drives
Klyball D-13
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