SYSTEM TECHNICAL MANUAL HARDWARE DESCRIPTION
Index
This interface signal is provided by the drive once each revolu
tion (16.67mS nom.) to indicate the beginning of the track.
This signal is normally logic zero (normally high) and makes
the transition to logical one to indicate Index. Only the trans
ition from high to low is valid.
Ready
This interface signal when a logic one together with Seek Com
plete, indicates that the drive is ready to read, write, or seek,
and that the I/O signals are valid. When this line is a logic zero,
all writing, reading, and seeking are inhibited. Ready shall be
inactive only as a result of and during recovery from a power
off condition or whenever the dc voltage monitor portion of
the Write Fault circuit is activated.
MFM Read Data
The data recovered by reading a pre-recorded track is trans
mitted to the host system via a differential pair of MFM Read
Data lines. The transition of the +MFM Read Date line going
more positive than the -MFM Read Data line represents a
flux reversal on the track of the selected head.
KEYBOARD
The low profile ASCII encoded keyboard is designed according to
NCR Corporate Appearance Plan (CAP) styling and newest ergo-
nometric requirements. It is connected to the system logic by a
four-wire twisted cable, non-extended length 0.5m.
Key arrangement consists of standard alpha keys, the 10-key
numeric keypad, cursor control keys, 20 programmable function
keys with escutcheon for function key description, and following
features:
• Automatic repeat entry on all data keys
• Rollover key feature for fast operation
• Double zero key
• Word processing mode (shift inversion lock for alpha keys
only)
• 8-byte FIFO buffer (plus 20 bytes on controller)
• Simple decimal point/comma exchange
The keyboard is currently available in two versions to provide
the languages shown in Figure 2.22.
2-31
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