UPD784915B Datasheet, PDF (42/86 Pages) NEC – 16-BIT SINGLE-CHIP MICROCONTROLLERS

µPD784915B, 784916B
(1) CTL amplifier/RECCTL driver
The CTL amplifier is used to amplify the playback control (PBCTL) signal that is reproduced from the CTL signal
recorded on a VCR tape.
The gain of the CTL amplifier is set by the gain control register (CTLM). Thirty-two types of gains can be set
in increments of about 1.78 dB.
The µPD784195 is also provided with a gain control signal generation circuit that monitors the status of the
amplifier output to perform optimum gain control by program. The gain control signal generation circuit generates
a CTL detection flag that identifies the amplitude status of the CTL amplifier output. By using this CTL detection
flag, the gain of the CTL amplifier can be optimized.
The RECCTL driver writes a control signal onto a VCR tape.
This driver operates in two modes: REC mode that is used for recording, and rewrite mode used to rewrite the
VISS signal. The output status of the RECCTL± pin is changed by hardware, by using the timer output from the
super timer unit as a trigger.
Figure 3-19. Block Diagram of CTL Amplifier and RECCTL Driver
ANI11
CTLDLY
RECCTL+
RECCTL-
CTL head
TOM1.4-TOM1.6
RECCTL driver
VREF
AMPC. 1
+
-
TM1-CR11 coincidence signal
TM1-CR13 coincidence signal
TM3-CR30 coincidence signal
CTLIN
CTLOUT1
CTLOUT2
AMPC. 1
+
-
Gain control signal
generation circuit
CTL detection flag L (AMPM0. 1)
CTL detection flag S (AMPM0. 3)
CTL detection flag clear (1 write to AMPM0. 6)
CTLM. 0-CTLM. 4
Waveform
shaping circuit
PBCTL signal (to timer unit)
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