Tandy 1000 Technical Reference Manual

Tandy 1000
(1) Read circuit
Technical Reference Manual
The read circuit consists of pre-amplifier, low pass filter, differenti-
ation amplifier, peak detector, time domain filter and read gate
(output driver) .
In read operation, the minute voltage induced by the read/write head is
amplified about 30dB by the pre-amplifier which is constructed with a
video band differential amplifier. Undesirable high frequency
noise is eliminated by the low pass filter (Ll, L2, C30, etc.) and the
read signal is supplied to the differentiation amplifier (Q3, Q4, LJ,
C3S, etc.).
The differentiation amplifier phase-shifts the peak position of the
reproduced waveform to the zero cross point, and at the same time,
further amplifies the signal about 20dB with the most appropriate
equalization. The peak detector which is constructed with a comparator
converts the differentiated output into a square wave.
The time domain filter eliminates a virtual pulse caused by the saddle
in the low frequency area (IF area, 62.5KHz, approx.) at outer tracks.
The time domain filter is constructed with two edge detectors, 2.4~8ec,
delay single shot (LSI pin 7, MS, C2l), data latch, and l~sec data
single shot (LSI pins 8 and 9, RAS, C22).
Then the signal is output from the FDD through the read gate, UJ (pins
9, 10, J-state output driver).
- J09 -

Tandy 1000 Specifications

General

Processor	Intel 8088
Processor Speed	4.77 MHz
RAM	128 KB (expandable to 640 KB)
Operating System	MS-DOS 2.11
Manufacturer	Tandy Corporation
Release Year	1984
Storage	Single or double 5.25" floppy disk drive (360 KB), optional hard drive
Sound	Tandy 3-voice sound
Ports	Parallel, Serial
Graphics	CGA (Color Graphics Adapter)
Graphics Modes	320x200, 640x200