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VISS (Index) Detect Mode: VISS detection is carried out by the VISS control circuit, which
counts 1 pulses in the PB-CTL signal. If the pulse count detects any value set in the VISS
interrupt setting bits (bits 5, 6, or 7 in the duty I/O register), an interrupt request is generated and
the duty I/O flag is cleared to 0.
At VISS record or rewrite, INDEX code is automatically written. INDEX code is composed of 0
continuous 62-bit data with 0 pulse data at both edge.
Examples of bit strings and the duty I/O flag at VISS detection/record is illustrated in figure 26.57.
Tape direction
Duty I/O flag
Tape direction
Duty I/O flag
Figure 26.57 Examples of VISS Bit Strings and Duty I/O Flag
Rev. 1.0, 02/00, page 710 of 1141
Thirty-two 1 pulses
detected
0
1 1 1 1
61±3 bits
63±3 bits
Start
(a) VISS detection (INDEX: Thirty-two 1 pulse setting)
1 2 3
0
1 1 1 1
Start
(b) VISS record
IRRCTL
1 1 1 1 0
IRRCTL
1 1 1 1 0
62 bits
64 bits
62 63 64
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