MEAD@usc-eclb.arpa (02/13/83)
From: Dick <MEAD@usc-eclb.arpa> I read an earlier message about problems with one of the MX80/buffered serial interface setups. I have suffered a similar problem using the Okidata 83A with a 2K buffered card sold by ASAP. I have looked at the card, it uses a Z80, 2716 eprom, and two 2114 rams, and a 8251 uart, with some support chips. I have dis-assembled the rom, and see no obvious cause for the problem. The problem I have (2 actually) is this: using the DTR handshake mode, I dump data to the printer, and at the point that the buffer shuts off the DTR, I lose some characters and get an overline(bug#1). Then, after the data has all been sent to the printer, the printer will continue to print out the buffer (same data) for two to three more passes. I seem to be getting the same last 527 characters that had been sent to the buffer. The overline/char loss may be due to the hardware, as the DTR handshake is done by re-writing the command byte to the 8251, toggling bit 2 (RTS or DTR or such), so I don't know if that can be fixed. But the looping buffer really gets me. Any one wanting to look over the prom code is welcome, if you have any good ideas. P.S. I checked using the built-in serial port and it works fine, but it only runs 1200 baud max and is not buffered, plus the OKIGRAPH option deletes it anyway, GRRR!!!! -------