HD404369 Datasheet, PDF (73/117 Pages) Hitachi Semiconductor – 4-bit HMCS400-Series microcomputer

HD404369 Series
Alarm Output Function
The MCU has a built-in pulse output function called BUZZ. The pulse frequency can be selected from the
prescaler S’s outputs, and the output frequency depends on the state of port mode register C (PMRC: $025).
The duty cycle of the pulse output is fixed at 50%.
Port Mode Register C (PMRC: $025): Four-bit write-only register that selects the alarm frequencies as
shown in figure 57. It is reset to $0 by MCU reset.
Port Mode Register A (PMRA: $004): Four-bit write-only register that selects D₃/BUZZ pin function as
shown in figure 51. It is reset to $0 by MCU reset.
BUZZ
Alarm output
controller
Alarm output
control signal
Port mode
register A
(PMRA)
Selector
2
System ^øPER
clock
Prescaler S (PSS)
Port mode
register C
(PMRC)
Figure 56 Alarm Output Function Block Diagram
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