ELSA TanGo 2000, Руководство пользователя

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Appendix
ELSA TanGo 2000
26
When uploading and downloading from/to BBS systems, a large number of
CRC errors result; in some cases the connection is even aborted. What are the
possible reasons?
CRC errors can have a variety of reasons. A possible cause is an incorrectly-set or missing handshake
process. In order to take proper advantage of data compression, the speed on the computer side should
be set higher than on the telephone side (e.g. 115,200 bps instead of 64,000 bps). This, however, requires
either a hardware- (RTS/CTS) or software-based (XON/XOFF) handshake process.
Both the software and the ISDN terminal adapter must use the same settings for these processes. CRC
errors may occur during data transfer if this is not the case. If you use RTS/CTS handshaking, the V.24
connection can also be the cause. When using a so-called mouse adapter (V.24 adapter from 25 to 9 pins),
it is also possible that the RTS and CTS conductors (Pin 4 and 5) in the adapter are not connected. One
should always ensure that V.24 cable adapters are fully wired for this reason.
The serial port of your computer can be a further source of errors. The use of a type 16550 UART chip is
advisable for speeds of 19,200 bps and higher under DOS and for general use under Windows and OS/2.
This UART has a 16 byte FIFO buffer which permits significantly higher transfer speeds. Type 8250 and
16450 chips only function reliably at speeds of up to 9600 bps; individual characters can be lost in the
interface at speeds of 19,200 bps upwards, leading to CRC errors.
Why do I always get CRC errors with my ISDN terminal adapter during ZModem
downloads at 115,200 bps, even though I'm using a UART 16550 with FIFO in my
COM port?
The throughput for CONNECTs at 64,000 bps is only around 6,000 cps
.
The poor throughput is the result of the large number of CRC errors. Check the BIOS settings of your
computer and ensure that IDE HDD BLOCK MODE is set to DISABLED.