On Mon, Oct 17, 2016 at 1:11 PM, Kurt McCullum <kurt.mccul...@att.net> wrote:
> John, Thanks for info. Is that a TELCOM limit? The reason I ask is because > when running virtual T with TS-DOS, I notice that the buffer can go to 255. > Or at least the byte which holds the buffer size. > > In my experience I've found that all 8-bit bytes go to 2^8 - 1 = 255 Just teasing :-) It could but it should never in practice have a value > 64. Have you observed a higher value than 64? It's not a limitation of TELCOM per se, it's a limitation of the receive interrupt handler logic and the size of the circular queue-on-array reserved for receiving bytes. The same receive handler is used for TELCOM and BASIC access to the serial port. See http://www.club100.org/ftp/m100-hiddenpowers-3.pdf Page 186 It shows a receive buffer of 64 bytes. If it went beyond the bounds, unmasked, I would expect it to corrupt other data structures. The high-water mark for the buffer is 40 (the point at which the receive handler sends XOFF), which probably makes more sense in the context of a 64 byte buffer than a 255 byte buffer :-) -- John.
