NEC NEC PD78081(A), User Manual

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CHAPTER 9 BUZZER OUTPUT CONTROL CIRCUIT
Internal Bus
f
XX
/2
9
f
XX
/2
10
f
XX
/2
11
TCL27 TCL26 TCL25
3
PM36
Selector
Timer Clock Select Register 2
Port Mode Register 3
BUZ/P36
P36
Output Latch
CHAPTER 9 BUZZER OUTPUT CONTROL CIRCUIT
9.1 Buzzer Output Control Circuit Functions
The buzzer output control circuit outputs 1.2 kHz, 2.4 kHz, 4.9 kHz, or 9.8 kHz frequency square waves. The buzzer
frequency selected with timer clock select register 2 (TCL2) is output from the BUZ/P36 pin.
Follow the procedure below to output the buzzer frequency.
(1) Select the buzzer output frequency with bits 5 to 7 (TCL25 to TCL27) of TCL2.
(2) Set the P36 output latch to 0.
(3) Set bit 6 (PM36) of port mode register 3 to 0 (Set to output mode).
Caution Buzzer output cannot be used when setting P36 output latch to 1.
9.2 Buzzer Output Control Circuit Configuration
The buzzer output control circuit consists of the following hardware.
Table 9-1. Buzzer Output Control Circuit Configuration
Item Configuration
Timer clock select register 2 (TCL2)
Port mode register 3 (PM3)
Figure 9-1. Buzzer Output Control Circuit Block Diagram
Control register