Having secured a copy of Tom Pittman's Tiny BASIC on paper tape (autographed by the man himself!), I'm in the process of adding a teletype simulator to the COSMAC Elf simulator. It's a bit strange because the 1802 code does bit-banged serial i/o, and my simulated teletype has to do bit-banged serial i/o back at it. At least initially, rather than hack all the 1802 code to run at a faster baud rate, I'm simulating 110 baud with my "teletype", so most of the time the emulated 1802 and the emulated teletype sit there waiting for each other to send data. It's _almost_ working, but I'm getting some odd results that I think may stem from an incomplete understanding of the way the ASR-33 and others of that vintage send and receive data. I'm testing with some code in an article about interfacing the Elf to a Teletype, so I'm pretty sure the Elf code is correct. I'm using 110 bits per second, no parity, 8 data bits, one low (logic 0) start bit, and one high (logic 1) stop bit. It seems to like the data low-order-bit first, but I have nothing that confirms that how it should work. I'm also working from the assumption that the data bits, the stop bit, and the start bit are all the same length. Also, I'm assuming that the "110 bits per second" includes the time for the stop and start bits, but I'm not sure of that either. It seems to be transferring characters; I get consistent hex values for each character I send to the Elf, but they seem to usually be either shifted left or right by one bit, or they have the high bit set when it shouldn't be. It feels like I've either added extra bits or am missing some in there somewhere. Can someone who knows this information for sure clear these things up for me? -Bill Richman (bill_r(a)inetnebr.com) http://incolor.inetnebr.com/bill_r - Home of the COSMAC Elf Microcomputer Simulator, Fun with Molten Metal, Orphaned Robots, and Technological Oddities.