– 22 –

CXA1372BQ/BS

DIRC (Pin 20) and 1 Track Jump

Normally, an acceleration pulse is applied for a 1-track jump. Then a deceleration pulse is given for a specified

time observing the tracking error from the moment it passes point 0, and tracking servo is turned ON again.

For the 100-track jump to be explained in the next item, as long as the number of tracks is about 100 there is

no problem. However a 1-track jump must be performed here, which requires the above complicated

procedure. For the 1-track jump in CD players, both the acceleration and deceleration take about 300 to

400µs. When software is used to execute this operation, it turns out as shown in the flow chart of Fig. 9.

Actually, it takes some time to transfer data.

Acceleration

Pulse waveform

Tracking error

Deceleration

$2C transfer latch

$28 transfer only

TZC

↓ ?

NO

YES

Latch

Timer (0.3ms)

$25 transfer latch

TR: REV

SL: OFF

TR: FWD

SL: OFF

Execute

Execute

TR: ON

SL: ON

Execute

$2C transfer latch

TZC

↓ ?

NO

YES

DIRC = L

Timer (0.3ms)

DIRC = H

TR: REV

SL: OFF

TR: FWD

SL: OFF

Execute

TR: ON

SL: ON

Fig. 9. 1-track jump not using DIRC (Pin 20)

Fig. 10. 1-track jump with DIRC (Pin 20)

Fig. 8. Pulse waveform and tracking error of 1-track jump

The DIRC (Direct Control) pin was provided in this IC to facilitate the 1-track jump operation. Conduct the

following process to perform 1-track jump using DIRC (normal High).

(a) Acceleration pulse is output. ($2C for REV or $28 for FWD).

(b) With TZC

↓ (or TZC ↑), set DIRC to Low. (SENS Pin 27 outputs "TZC"). As the jump pulse polarity is

inverted, deceleration is applied.

(c) Set DIRC to High after a specific time.

Both the tracking servo and sled servo are switched ON automatically.

As a result, the track jump turns out as shown in the flow chart of Fig. 10 and the two serial data transfers

can be omitted.