[HN Gopher] UP9600: How to Bit-Bang 9600 Baud RS-232 on the C64
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       UP9600: How to Bit-Bang 9600 Baud RS-232 on the C64
        
       Author : zdw
       Score  : 67 points
       Date   : 2022-03-08 14:49 UTC (8 hours ago)
        
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 (TXT) w3m dump (www.pagetable.com)
        
       | snvzz wrote:
       | This is a very cool way to actually use the CIA's serial port.
       | But this also means it is technically not bit-banging.
       | 
       | Ironically, bit-banging is what the C64's "KERNAL" does by
       | default in its rs232 implementation.
        
       | johnklos wrote:
       | Interestingly, the 6551 (and later 8551) are used on the
       | Commodore Amiga A2232 seven port serial card. Seven of them are
       | run by a 3.58 MHz 65CE02 at up to 19200 baud, although the card
       | can be modified to run all ports simultaneously at 57600 baud, or
       | two ports at 115200 baud. Because the 65CE02 does all the work,
       | there's almost no overhead for the host Amiga. It's a versatile
       | chip!
       | 
       | The fact that the C64 and friends can emulate a 6551 is
       | impressive. That they can emulate it up to 9600 baud with unused
       | shift registers, on the other hand, is awe inspiring.
        
       | Scoundreller wrote:
       | > TTL-level RS-232
       | 
       | I ran 115k2 for a couple years directly between an atmel 8515
       | (sending TTL) and a Pentium2 motherboard (sending +12/-12) 24/7
       | for a couple years with no ill effects.
        
         | monocasa wrote:
         | atmels are known to be tanks wrt to overvoltage protection. IMO
         | half the success of the arduinos is that their atmel's pads can
         | even handle children. Few chips are so tolerant.
        
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       (page generated 2022-03-08 23:01 UTC)