Apologies for the longish post, didn't have time to write a short one! *TL;DR* I've been happily serial printing on my 100/102, but my 200 doesn't work, so I'm in search of a non-hardware solution to tying DTS/RTS together on a 200 to let it send RS-232 data. -------- I've been experimenting with RS232 printing on an Apple Imagewriter ii, and I noticed that my 100's and 102 will print to it just fine, but my two 200's both just time out trying to print (by print I mean, save a text file to "com:88n1enn". Same deal when just playing around in the terminal, it gets a little buggy and I can't even quit without powering on and off, and identical behavior on both otherwise healthy 200's. What gives?
I dug around the m100 list archives, and there's this thread from 2015 http://lists.bitchin100.com/htdig.cgi/m100-bitchin100.com/2015-January/069836.html that's very similar (also this one <http://lists.bitchin100.com/htdig.cgi/m100-bitchin100.com/2018-May/077378.html> and this one <http://lists.bitchin100.com/htdig.cgi/m100-bitchin100.com/2013-January/065432.html>, an old problem). So I hooked my 102 and 200 up to a scope and made a little test harness to look around, and long story short, the 200 indeed refuses to send any RS232 data unless RTS/CTS are tied together. This doesn't seem to be the case for the 100 and 102, which will happily send data out blind. Digging through the Technical Reference Manual <https://ia801908.us.archive.org/14/items/Model_200_Technical_Reference_Manual_1986_Tandy/Model_200_Technical_Reference_Manual_1986_Tandy.pdf>, the 200 does indeed have a different chip (82C51A) for handling serial IO, and perhaps it is pickier about when it allows outbound traffic. The TRM has what amounts to a decent data sheet on that chip, and this part caught my eye (bottom of pdf page 98): [image: image.png] It seems like perhaps it's possible to fix this with software? Or, am I way overthinking this whole thing, and there's another way to do it that's even easier? I know I can just get a null modem cable, but it's kind of a bummer to have to get all new cables to use a 200 with printers the 100/102 happily connected to. Thanks for reading / any advice. -Charlie
