rankins@argentina.crd.ge.com (raymond r rankins) (05/31/90)
The following is a problem we are having using hardware flow control on the Sun workstation serial ports. If anyone has experienced similar problems, and hopefully resolved it in some way, please let us know. You can email to either myself (rankins@argentina.crd.ge.com) or to cannon@bahamas.crd.ge.com. Thanks. -------------------------------------------------------------------- In an application we are attempting to use hardware flow control (RTS/CTS) between a Sun and a PC. On the PC side we are using a commercial library of routines which appear to work properly in managing the line. On the Sun side, however, we have discovered two conditions which are causing us some grief. 1) Sun has not implemented HW flow control on the receiving side in their serial line drivers for ttya and ttyb: RTS is not lowered when the buffer becomes nearly full. We had heard that flow control had been implemented in the driver on the first 4 ports of the ALM board. We have an ALM board and have tried to test this. In doing so, however, we ran into problem number two below. 2) When we configure the device for HW flow control, the C read behaves improperly. It appears that if there is a full buf (as defined in the man page on read) of data in the input buffer then the read will do fine. If there is not a full buffer (i.e. if it can't read nbytes of data), it will block on the read. With this (probably unrelated) bug we couldn't test the ALM and the driver for flow control. In an attempt to diagnose problem #2 above we tried software flow control using the ALM and that didn't work either. The C read command would still block if buf was not full. Ray Rankins |(518) 387-7340 | INTERNET: rankins@argentina.crd.ge.com 2 Moonglow Rd. |(518) 583-3320 | COMPUSERVE: 71131,3236 Gansevoort, NY 12831 | | AmericaOnline: RayRankins