Rev. 1.0, 02/00, page 710 of 1141
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.
0
Tape direction
Duty I/O flag
(a) VISS detection (INDEX: Thirty-two 1 pulse setting)
1
1
1
1
61±3 bits
Thirty-two 1 pulses
detected
IRRCTL
63±3 bits
Start
1
1
1
1
0
0
Tape direction
Duty I/O flag
(b) VISS record
1
1
1
1
62 bits
IRRCTL
64 bits
Start
1
1
1
1
0
1
2
3
62 63 64
Figure 26.57 Examples of VISS Bit Strings and Duty I/O Flag