Main Status Register (Port FB7E)
b0..3 DB FDD0..3 Busy (seek/recalib active, until succesful sense intstat) b4 CB FDC Busy (still in command-, execution- or result-phase) b5 EXM Execution Mode (still in execution-phase, non_DMA_only) b6 DIO Data Input/Output (0=CPU->FDC, 1=FDC->CPU) (see b7) b7 RQM Request For Master (1=ready for next byte) (see b6 for direction)
Status Register 0
b0,1 US Unit Select (driveno during interrupt) b2 HD Head Address (head during interrupt) b3 NR Not Ready (drive not ready or non-existing 2nd head selected) b4 EC Equipment Check (drive failure or recalibrate failed (retry)) b5 SE Seek End (Set if seek-command completed) b6,7 IC Interrupt Code (0=OK, 1=aborted:readfail/OK if EN, 2=unknown cmd or senseint with no int occured, 3=aborted:disc removed etc.)
Status Register 1
b0 MA Missing Address Mark (Sector_ID or DAM not found) b1 NW Not Writeable (tried to write/format disc with wprot_tab=on) b2 ND No Data (Sector_ID not found, CRC fail in ID_field) b3,6 0 Not used b4 OR Over Run (CPU too slow in execution-phase (ca. 26us/Byte)) b5 DE Data Error (CRC-fail in ID- or Data-Field) b7 EN End of Track (set past most read/write commands) (see IC)
Status Register 2
b0 MD Missing Address Mark in Data Field (DAM not found) b1 BC Bad Cylinder (read/programmed track-ID different and read-ID = FF) b2 SN Scan Not Satisfied (no fitting sector found) b3 SH Scan Equal Hit (equal) b4 WC Wrong Cylinder (read/programmed track-ID different) (see b1) b5 DD Data Error in Data Field (CRC-fail in data-field) b6 CM Control Mark (read/scan command found sector with deleted DAM) b7 0 Not Used
Status Register 3
b0,1 US Unit Select (pin 28,29 of FDC) b2 HD Head Address (pin 27 of FDC) b3 TS Two Side (0=yes, 1=no (!)) b4 T0 Track 0 (on track 0 we are) b5 RY Ready (drive ready signal) b6 WP Write Protected (write protected) b7 FT Fault (if supported: 1=Drive failure)
== Motor On/Off Flipflop ==