UPD17015 datasheet(42/120 Pages) NEC

42 / 120 page

µPD17015

10.2.2

Basic Timer 0 Carry Flip-Flop, Basic Timer 1 Carry Flip-Flop, BTM0CY Flag, and BTM1CY Flag

The flip-flop is set at constant intervals, and its state is detected using the BTM0CY and BTM1CY flags.

The BTM0CY and BTM1CY flags are read-only. These flags are reset by reading their contents using the

instructions listed in Table 10-1 (Read & Reset).

The BTM0CY and BTM1CY flags are “0” at a power-on reset. It becomes “1” at a CE reset. So, it can be used

as a power failure detection flag.

Even when power is supplied, the BTM0CY and BTM1CY flags will not be set until their contents have been read

using the instructions listed in Table 10-1. Once a read instruction is executed, the flag is set at constant intervals.

Fig. 10-2 shows the configuration and function of the basic timer 0 carry flip-flop judge register. Fig. 10-3 shows

the configuration and function of the basic timer 1 carry flip-flop judge register.

Table 10-1 Instructions Used to Reset the BTM0CY and BTM1CY Flags

Note

When the low address of m is 6H, and 0EH or 0FH is written into r.

Remark m = 6EH or 6FH

Mnemonic

Operand

Mnemonic

Operand

ADD

ADDC

SUB

SUBC

AND

r, m

m, #n4

XOR

SKE

SKEG

SKT

SKLT

SKF

m, #n

SKNE

MOV

@r, m

m, @rNote

UPD17015 Datasheet(PDF) 42 Page - NEC