Rev. 1.0, 02/00, page 579 of 1141
Cleared
Cleared
Reset
Value set in reference
period register 1 (RFD)
Counter
Value set in REF30
counter register (RFC)
External sync
signal
REF30
REF30P
Figure 26.12 Generation of REF30 Signal by the External Sync Signal
•
CREF Signal Generator
The CREF signal generator generates the CREF signal which is the reference signal to
control the phase of capstan.
To generate the CREF signal, set the 1/2 the reference period to the reference period
register 2 (CRF). If the set value matches the counter value, a toggle waveform is
generated corresponding to the 50 percent duty cycle, and a one-shot pulse is output at each
rising edge of the waveform. The counter of CREF signal generator is initialized to H'0000
and the phase of the toggle is cleared to L level when the mode shifts from PB (ASM) to
REC. The timing of clearing is selectable between immediately after the transition from
PB (ASM) to REC and the timing of DVCFG2 after the transition. Use bit 3 (CRD) of the
reference period mode register (RFM) for this selection.
In the capstan phase error detection circuit, either REF30 signal or CREF signal can be
selected for the reference signal. Use either of them according to the use of the system.
Use the CREF signal to control the phase of the capstan at a period which is different from
the period used to control the phase of the drum. For the switching between REF30 and
CREF in the capstan phase control, see the description of capstan phase error detection
control register (CPGCR) in section 26.9.4, Register Description.