HD63265 Floppy Disk Controller Users Manual 2ed Mar89 - Bitsavers

Seek Completion: After all the calculated number of step pulses have beenoutput, SSBO's SED (seek end) bit is set after the step rate time specified bythe SPECIFY command following the last step pulse output. The number of thedrive which terminates the seek is then set in USO and USI of SSBO. Followingthis, the command terminates normally and the CHECK INTERRUPT STATUS commandis requested by setting the IRQ signal active. Additionally, when HDIR=O,if TRKO becomes active, the step pulse output is halted prematurely.Following this, as described in the previous paragraph, the SED, usa, andUSI bits of SSBO are modified and the command normally ends with an interruptrequest to the host for issuing a CHECK INTERRUPT STATUS command.At this time, the result parameter PCN of the CHECK INTERRUPT STATUScommand is the same as the command parameter NCN value of the SEEK command,and is not always HEX 00. The TRKO signal is latched 500 ns (8" mode) orI ~s(5" mode) before the step pulse output.Parallel Seek: The FDC is placed into the command waiting state when the steppulse output begins after receiving the SEEK or RECALIBRATE command. At thistime, another SEEK or RECALIBRATE command can be issued for a new drive whosedrive seek bit in the status register is zero.Head Unload: The head must be unloaded (HLOAD 0) immediately after the SEEKcommand is issued. However, if the SEEK command is issued for a drive whosehead is loading and parameter NCN is equal to PCN, the command is terminatedwithout head unload.Note:If the SEEK command is issued to a drive which is not ready, the statusregister's drive seek bit is not set.58 HITACHI