Bit Description Of The Fdc Main Status Register - NEC Advanced Personal Computer System Reference Manual

Controller PCB
Table 3-7 Bit Description of the FDC Main Status Register
BIT
NUMBER NAME
SYMBOL
DESCRIPTION
DBO
FDD A Busy DAB FDD A is in the Seek Mode.
DBI FDD B Busy DBB
FDD B is in the Seek Mode.
DB2 FDD C Busy DCB Not used.
DB3
FDD D Busy DDB Not used.
DB4 FDC Busy CB A read or write command is in
process.
DB5 Non-DMA
NDM The FDC is in the Non-DMA
Mode Mode.
DB6 Data Input/ DIO Indicates direction of data transfer
Output between the FDC and the proces-
sor. DIO
=
'1' indicates transfer is
from FDC data register to the
processor; DIO
=
'0' indicates
transfer is from processor to FOC
data register.
DB7 Request for RQM Indicates Data Register is ready to
Master send or receive data to or from the
processor. Both bits DIO and RQM
should be used to perform the
handshaking functions of "ready"
and "direction" to the processor.
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