fd 1797-register-usage 19871016/wjvg +0 = fdc command/status type 1 commands w ......00 = 6 ms stepping rate w ......01 = 12 ms stepping rate w ......10 = 20 ms stepping rate w ......11 = 30 ms stepping rate w .....1.. = verify track# w ....1... = load/-unload head at beginning w 0000.... = restore (seek track00) w 0001.... = seek track# in data-reg w ...1.... = update track register w 001..... = step (in same direction as previous) w 010..... = step-in (to track76) w 011..... = step-out (to track00) type 2 commands w ......1. = enable side compare w .....1.. = 15 ms delay w ....1... = compare for side 1/-0 w ...1.... = multiple records w 100....0 = read sector w .......1 = f8(deleted dam)/-fb(dam) w 101..... = write sector type 3 commands w .....1.. = 15 ms delay w 11000.00 = read adres w 11100.00 = read track w 11110.00 = write track type 4 commands w .......1 = not ready to ready transition w ......1. = ready to not ready transition w .....1.. = index pulse w ....1... = immediate interrupt, requires reset w ....0000 = terminate with no interrupt w 1101.... = force interrupt status type1 type2,3 r .......1 = busy busy r ......1. = index pulse data request r .....1.. = track0 lost data r ....1... = crc error crc error r ...1.... = seek error record not found r ..1..... = head loaded read sector: record type write : write fault r .1...... = write protect write protect r 1....... = drive not ready drive not ready +1 rw = fdc track +2 rw = fdc sector +3 rw = fdc data (of gewenste track) also in the cs-systeem: +4 w = fdc drive select etc. w .......0 = drive0 w ......0. = drive1 w .....0.. = drive2 w ....0... = drive3 w ...1.... = side0 w ..1..... = double density .x...... = not used w 0....... = trigger headload delay end