On Wed, 07 May 2008 16:34:48 -0400 James Knott <[EMAIL PROTECTED]> wrote:
> Jerry Feldman wrote: > > On Wed, 07 May 2008 15:43:43 -0400 > > James Knott <[EMAIL PROTECTED]> wrote: > > > > > >> That should read "It doesn't change anything on the receiver..." > >> > > > > Agreed. It only really means something to the modems themselves. > > > > > It only set the transmitted stop bits and nothing else. That applies to > terminals, computers, monitors etc. It simply allows sufficient time > for the receiver to stop receiving one character and start waiting for > the next. Try to send 12-bit words in an 8-bit environment without UARTS :-) In any case, the ASCII ASYNCHRONOUS protocol would send 1 byte at a time delimited by a stop and a start bit and optionally a half of full bit. The stop and stat bits were, as you mentioned, timing so that the data could be recognized. In contrast, synchronous protocols, such as IBM's bisynch and more modern protocols would send blocks of data delimited by special control characters, but these protocols required some extra hardware, but did not require start and stop bits. Back when we were doing the design for the POS, the cost of using the bisynch protocol came to about $50.00/unit or $50,000. In this case, we were building the modem into the device, and we may or may not have had a UART (I don't remember exactly when they became available). -- -- Jerry Feldman <[EMAIL PROTECTED]> Boston Linux and Unix PGP key id: 537C5846 PGP Key fingerprint: 3D1B 8377 A3C0 A5F2 ECBB CA3B 4607 4319 537C 5846
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