Tandy 1000 SL Technical Reference Manual page 180

NEC
TC (Terminal Count)
When theTC input is high, it indicates the termination of
a DMA transfer. It terminates data transfer during Read/
Writelscan commands in DMA or interrupt mode.
IDX(lndex)
The IDX input goes high at the beginning of adisk track.
INT (Interrupt)
The INToutput is FDC's interrupt request.
CLK (Clock)
CLK is the input for the FDC's single-phase, 8 MHz
squarewave clock.
WCK (Write Clock)
The WCK input sets the data write rate to the FDD. It is
500 kHz for FM, 1 MHz for MFM drives, with a 250 ns
pulse for both FM and MFM.
RDW (Read Data Window)
The ROW input is generated by the phase-locked loop
(PLL). It is used to sample data from the FDD.
RDD (Read Data)
The RDD input is the read data from the FDD, containing
clock and data bits.
WDA(Write Data)
WDA is the serial clock and data output to the FDD.
WE (Write Enable)
The WE output enables writedata into the FDD.
vco (vco
Sync)
The VCO output inhibits the VCO in the PLL when low,
enables it when high.
MFM (MFM Mode)
The MFM output shows the FDDs mode. It is high for
MFM, low for FM.
HD(Head Select)
Head 1 is selected when the HD output is 1 (high), head 0
is selected when HD is 0 (low).
USO, U s (Unit Select 0,l)
The
US0
and US1 outputs select the floppy disk drive
unit.
PSO, P s (Preshift 0,l)
The PSo and PSI outputs are the write precompensation
status for MFM mode. They determine early, late, and
normal times.
RDY (Ready)
The RDY input indicates that the FDD is ready to receive
data.
HDL (Head Load)
The HDL output is the command which causes the
readlwrite head in the FDD to contact the diskette.
FLTlTRO (FaultlTrack 0)
In the readlwrite mode, the FLT input detects FDD fault
conditions. In the seek mode, TRO detects track 0.
WPlTS (Write ProtectlTwo Side)
In the readlwrite mode, the WP input senses write pro-
tected status. In the seek mode, TS senses two-sided
media.
FRlSTP (Fault ResetlStep)
In the readlwrite mode, the FR output resets the fault
flip-flop in the FDD. In the seek mode, STP outputs step
pulses to move the head to another cylinder. A fault re-
set pulse (FR) is issued at the beginning or each Read or
Write command prior to the HDL signal.
LCTlDlR (Low CunentlDirection)
In the readlwrite mode, the LCT output lowers the write
current on the inner tracks. In the seek mode, the DIR
output determines the direction the head will move in
when it receives a step pulse.
W l S E E K (ReadlWritelSeek)
The m l S E E K output specifies the readlwrite mode
when low, and the seek mode when high.
GND(Ground)
Ground.
VCC(+5v)
+5 V power supply.
6-5