Vfo Interface Signals; Modified Frequency Modulation Mode; Vfo Synchronization (Syc); Standardized Read Data (Srd) - NEC FD1165 Maintenance Manual

/ DISK CHANGE
DOOFl CLOSE
I
OPEN
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CLOSE
DRIVE
SELECT
DISK
CHANGE
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Figure 3-8 Disk Change Signal Timing
3.5 VFO INTERFACE SIGNALS
The optional VFO interface signals are described in the
following sections.
3.5.1 Modified Frequency Modulation Mode (MFM)
The MFM signal is Low when MFM data is read or written. The
line is High whenFM data is read or written.
3.5.2 VFO Synchronization (SYC)
The SYC signal goes Low when read data is synchronized by
the VFO circuit.
3.5.3 Standardized Read Data (SRD)
The SRD line conveys Standardized Read Data. The data is
synchronized by the VFO circuit to make it easily and more
reliably read.
3.5.4 Window (WID)
The controller uses the WID signal to distinguish between
clock pulses and data output by phase-matching the Window
signal with the Standardized Read Data signal. Figure 3-9
shows the timing relationship between the signals. Once the
data splice point is passed, timing becomes irregular until
the VFO is resynchronized.
3-9