
— Braking period (c)
This period ends when the WRQ signal rises, i.e. at the point subcodes can be read. If WRQ does not go high,
the period is terminated if 60 ms elapse.
Note: Since sled forwarding is not performed, a sled forwarding operation is necessary for large track jumps.
Arbitrary track jump mode is initialized by the following 2-byte command.
The lower 6 bits of the data byte set the track jump acceleration period (a) and the track jump deceleration period
(b). The period a is calculated from the given n and rounded to an integer. The LC78631E monitors the TES half
period and terminates the b period if a period longer than the set period elapses.
The TES half period for b period termination is
≈ (123 × d3) + (62 × d2) + (32 × d1) + (17 × d0) s
Note: * The maximum value (306 s) is set when [d3 d2 d1 d0] = [0 0 0 0].
Track check mode
The LC78631E will count the specified number of tracks when the microprocessor sends an arbitrary binary value
in the range 8 to 254 and either a track check in or a track check out 2-byte command.
No. 5342-17/34
LC78631E
DATA BYTE + $48
ARBITRARY TRACK JUMP MODE SET COMMAND
d5
d4
Track jump acceleration period
0
(8/16)
× n tracks
0
1
(9/16)
× n tracks
1
0
(10/16)
× n tracks
d3
d2
d1
d0
TES half period
0
306 s*
0
1
17 s
0
1
0
32 s
0
1
0
62 s
1
0
123 s
Code
Command
RES = low
$F0
TRACK CHECK IN
$F8
TRACK CHECK OUT
$FF
TRACK CHECK CLEAR
q