GM82C803CN Datasheet, PDF (58/84 Pages) List of Unclassifed Manufacturers – 2.88 MB FDC/ Dual UARTs with FIFO/PIO(EPP/ ECP)/ IDE Interface/ S-IR/ PnP

GM82C803CN
EIS
: Enable implied Seek. When set to 1 the FDC will perform a Seek operation before executing a read or write
command. Defaults to no implied seek.
EFIFO : A 1 puts the FIFO into the NEC765 compatible mode where the FIFO is disabled. This means data transfers
are asked for on a byte by byte basis. Defaults to 1, FIFO disabled. The threshold defaults to 1.
POLL : Disable polling of the drives. Defaults to 0 polling enabled. When enabled, a single interrupt is generated af-
ter a reset. No polling is performed while the drive head is loaded and the head unload delay has not expired.
FIFOTHR : The FIFO threshold in the execution phase of read or write commands. This is programmable from 1 to 16 b-
ytes. Defaults to one byte. A 00H selects one byte, FH selects 16bytes.
PRETRK : Pre-compensation start track number. Programmable from track 0 to 255. Defaults to track 0.. A 00H selects
track 0. FFH selects 255.
Dumpreg
This command is designed to support system run-time diagnostics and application software development and debug.
Invalid
If an Invalid command is sent to the FDC( a command not defined above), then the FDC will terminate the command after
bits 7 and 6 of Status Register 0 are set to 1 and 0 respectively. No interrupt is generated during this condition. Bits 6 and 7
(DIO and RQM) in the Main Status Register are both 1, indicating to the Host that the FDC is in the result phase and the
contents of Status Register 0 must be read. When the Host reads Status Register 0, it will find an 80H indicating an Invalid
command was received. A Sense Interrupt Status command must be sent after a Seek or Recalibrate interrupt: otherwise
the FDC will consider the next command to be an invalid command. In some applications, the user may wish to use this
command as a No-Op command to place the FDC in a standby or No Operation state.