kenn at bluetree.ie
Sat Sep 9 16:43:25 IST 2000
> ISDN TAs connected to a PC's serial port offend my engineer's
> soul. ISDN is
> a synchronous technology. There are no start and stop bits (so 1000 bits
> down an ISDN line = 125 bytes of data, whereas 1000 bits of data down an
> RS-232 cable = 100 bytes of data). So, a PC using a serial TA is busily
> converting an 8 kbyte/s data stream into asynchronous serial
> data, which is
> being re-converted into synchronous data by the TA. This leads to poorer
> latency figures with a serial TA than with a PCI/ISA ISDN card.
Well, to be fair, this conversion should be happening on
a byte-by-byte basis, therefore the additional latency should
be of the order of a byte time, ie (1/11520) = 87uS.
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