HP41 FI data line - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: General Forum (/forum-4.html) +--- Thread: HP41 FI data line (/thread-5653.html) |
HP41 FI data line - Nate Martin - 02-07-2016 09:20 PM Should the FI data line go high or low to indicate data available? FI line from the I/O ports? Thanks, Nate RE: HP41 FI data line - Diego Diaz - 04-13-2016 09:36 AM Hi Nate, In short, no, FI is the Flag Input line. I'll add that this is the obscurest and most poorly documented line from the I/O interface. :-) It's used only by peripherals (PRINTER, HP-IL, WAND, etc) when requesting service from the CPU and is held high for a full digit time (four clock bit time cycles). The exact digit when the FI line is high informs the CPU of the type of service/periphera requesting service. To the best of my knowledge, apart from said peripherals, only the CL CPU (for obvious reasons) and the USB-41 (to simulate 82143A printer) handle this line. It has no use on ROM pacs or any other module. Cheers from Canary Islands. Diego. |