UPD4991ACX データシートの表示（PDF） - NEC => Renesas Technology

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UPD4991ACX

4-BIT PARALLEL I/O CALENDAR CLOCK

NEC => Renesas Technology 

µPD4991A

FUNCTION OUTLINE

• The µPD4991A has the following three modes:

1 BASIC TIME MODE

In this mode, data can be written and read between the timer counter and the CPU. Moreover, control

registers 1 and 2 can be specified by a command*.

2 ALARM SET & TP1 CONTROL MODE

In this mode, data is set to the alarm register, the function of TP1 is set, and control registers 1 and 2 are

specified by a command*.

3 ALARM SET & TP2 CONTROL MODE

In this mode, data is set to the alarm register, the function of TP2 is set, the 12- or 24-hour mode is selected,

leap year identification function is set, and control registers 1 and 2 are specified by a command*.

* Control registers 1 and 2 are commonly used in all the modes.

To select a mode, write mode data to ADDRESS = “FH.” Once a mode has been set, it is retained until a new

mode is set.

Table 1 shows the correspondence between modes and mode data.

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