Tandy 1000 HX Technical Reference Manual page 202

SEC
M
PD765A/
M
PD7265
TC (Terminal Count)
When the TC input is high, it indicates the termination of
a DMA transfer. It terminates data transfer during Read/
Write/Scan commands in DMA or interrupt mode.
IDX (Index)
The IDX input goes high at the beginning of a disk track.
INT (Interrupt)
The INT output 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 RDW 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 write data into the FDD.
VCO(VCOSync)
The VCO output inhibits the VCO in the PLL when low,
enables it when high.
MFM (MFM Mode)
The MFM output shows the FDD's 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).
UScUSi (Unit Select 0,1)
The US
0
and US
1
outputs select the floppy disk drive
unit.
PSo,PSi(PreshiftO,1)
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
read/write head in the FDD to contact the diskette.
FLT/TRO (Fault/Track 0)
In the read/write mode, the FLT input detects FDD fault
conditions. In the seek mode, TR0 detects track 0.
WP/TS (Write Protect/Two Side)
In the read/write mode, the WP input senses write pro-
tected status. In the seek mode, TS senses two-sided
media.
FR/STP (Fault Reset/Step)
In the read/write 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.
LC17 DIR (Low Current/ Direction)
In the read/write 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.
RW/SEEK (Read/Write/Seek)
The RW/SEEK output specifies the read/write mode
when low, and the seek mode when high.
GND (Ground)
Ground.
V
CC
(+5V)
+5 V power supply.