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2015-12-0001

PT0280-8

12/11/15

9

PT7C43390/43390C

Real-time Clock Module

2.2. Configuration of Command

8 types of command are available for the RTC. The RTC reads / writes the various registers by inputting these fixed codes and

commands. The RTC does not perform any operation with any codes and commands other than those below. However, in case that

the fixed codes or the commands are failed to be recognized in the 1st byte but are successfully recognized in the 2nd and higher

bytes, the commands are executed.

*1. Write only flag. The PT7C43390 initializes by writing "1" in this register.

*2. Scratch bit. This is a register which is available for read / write operations and can be used by users freely.

*3. Read only flag. Valid only when use the alarm function. When the alarm time matches, this flag is set to "1", and it is cleared

to "0" when reading.

*4. Read only flag. "POC" is set to "1" when power is applied. It is cleared to "0" when reading. Regarding "BLD", refer to "Low

Power Supply Voltage Detection Circuit".

*5. Test bit. Be sure to set "0" in use.

*6. No effect when writing. It is "0" when reading.

3. Configuration of Registers

3.1. Real-time Data Register

The real-time data register is a 7-byte register that stores the data of year, month, day, day of the week, hour, minute, and second

in the BCD code. To write / read real-time data 1 access, transmit / receive the data of year in B7, month, day, day of the week,

hour, minute, second in B0, in 7-byte. When you skip the procedure to access the data of year, month, day, day of the week, read /

write real-time data 2 accesses. In this case, transmit / receive the data of hour in B7, minute, second in B0, in 3-byte.

The RTC transfers a set of data of time to the real-time data register when it recognizes the read command.

Therefore, the RTC keeps precise time even if time-carry occurs during the read operation of real-time data register.