NEC Advanced Personal Computer System Reference Manual page 91

Controller PCB
Table 3-8 FDC Symbols (cont'd)
SYMBOL NAME
DESCRIPTION
R Record Specifies the sector number, which is
read or written.
R/W Read/Write
Specifies the Read (R) or Write (W)
signal.
SC Sector
Indicates the number of sectors per
cylinder.
SK Skip Specifies the Skip Deleted Data Address
Mark.
SRT
Step Rate Time Specifies the Stepping Rate for the FDD
(1
to 16 ms in I-ms increments).
ST
°
Status 0 Specifies which of four registers will
ST 1 Status 1
store the status information after a
ST 2 Status 2
command has been executed. This
ST 3 Status 3
information is available during the result
phase after command execution. These
registers should not be confused with the
main status register (selected by AO
=
0).
ST 0 to 3 can be read only after a
command has been executed. They
contain information relevant to that
particular command.
STP
Scan Test
During a Scan operation, if STP
=
1, the
data in contiguous sectors is compared
byte by byte with data sent from the
processor (or DMA). If STP
=
2, then
alternate sectors are read and compared.
USO, Unit Select
Specifies the selected drive number.
USI
3-26