On 05/09/2018 01:26, Jim Brain wrote: > It works as designed. /16 mode gives 115200. The T232 used this to > get 115200 and 230400 (by using the 6551A and double clocking it) > Whoever wrote the data sheet seemed to think the /16 mode is only for working with synchronous TxC (XTAL1) and not an asynchronous with an external crystal (XTAL1 + XTAL2). "On-chip baud rate generator: 15 programmable baud rates from a standard 1.8432 Mhz external crystal (50 to 19,200 baud)." "External 16x clock input for non-standard baud rates (up to 125Kbaud)" I can't tell what the person who designed the chip was thinking, but it's rather telling that both commodore and apple don't appear to have been aware of it when they wrote their drivers. I admit my electronics knowledge is a little poor, so I have no idea what xtal2 input is and what the chip will do if you put it into a mode where it would normally be ignored. I've been trying to find out when this was discovered, a2232tuning.lha is the earliest so far and 1.4 is from 1997. I found this rather interesting post however. "> The Super Serial Card came with a faulty 6551. You can > get it replaced from the people who make the TurboASB. Ah, I know what the problem is. The 6551 is not "faulty". The problem is that the 6551 has a peculiar design feature: if the incoming flow control signal (CTS) turns off, the transmitter is immediately disabled, causing a character being transmitted to be cut off, producing a garbage character at the other end. This applies to the original Rockwell R6551, and possibly to some second sources. The Rockwell R65C51 (CMOS version) and other second sources of the 6551 will wait until the current character is completely sent before stopping transmit in response to CTS going away. The outgoing flow control signals cause similar problems (on all versions): dropping RTS will immediately cut off the transmitter, but this can be managed by waiting for the current character to be completely sent before RTS is dropped. The replacement 6551 provided with the TurboASB will behave like the R65C51, so hardware handshaking doesn't cause data corruption."Received on 2018-09-05 10:00:04
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