SM8578BV Просмотр технического описания (PDF) - Nippon Precision Circuits
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SM8578BV Datasheet PDF : 16 Pages
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SM8578BV
Clock and Calendar Registers (Registers 0 to 6)
I Data is in BCD format. For example, register 0 data “0101 1001” represents the value 59 seconds. Also, “*”-
entries in the register table represent read/write locations that can be used as RAM.
I Clock timing is in 24-hour mode.
I Year register and leap year:
The year register represents years as 2 digits, with 00 following year 99.
Leap years are automatically identified for years up to 2099.
I Day-of-week register:
The day-of-week register is a 7-bit register (bits 0 to 6) with valid values shown in the following table.
Note that a register setting with a multiple number of “1” bits is invalid.
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
Day-of-week
0
0
0
0
0
0
1
Sunday
0
0
0
0
0
1
0
Monday
0
0
0
0
1
0
0
Tuesday
0
0
0
1
0
0
0
Wednesday
0
0
1
0
0
0
0
Thursday
0
1
0
0
0
0
0
Friday
1
0
0
0
0
0
0
Saturday
I FOS (Abnormal Oscillation Detection Bit)
This flag reports oscillation abnormalities during normal operation, such as may occur when the supply volt-
age falls too low, for example. It is set to “1” to indicate abnormal oscillation, and maintains this value until
a “0” bit is written. It is not affected by the function of any other bits.
I fr (Read Flags)
When CE is HIGH, these flags are set to “1” when the 1s seconds digit is incremented. They are set to “0”
when CE goes LOW. This makes it possible to determine whether the 1s seconds digit has been incremented
during a clock register read-out operation (when CE is HIGH). If the fr bits are set to “1”, all the clock tim-
ing registers should be read again.
The seconds and year registers do not have fr flags. Instead, bits 6 and 5 in the seconds register and bits 7 and
6 in the year register are logically-Ored with data “1” (example: year register 00101001 → 11101001).
When CE goes LOW, the register values are restored (example: year register 11101001 → 00101001).
NIPPON PRECISION CIRCUITS INC.—7
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