RF5C62 データシートの表示（PDF） - RICOH Co.,Ltd.

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RF5C62

REAL-TIME CLOCK

RICOH Co.,Ltd. 

RP/RF/RS5C62

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Questions and Answers

Question 5 : An attempt to disable a cyclic interrupt by setting the CTFG bit to “0” in the control regis-

ter 2 results in holding the INTR pin output low. What is the cause of this phenomenon?

Answer 5: As in Answer 4 above, this phenomenon may occur when an alarm interrupt and a cyclic inter-

rupt are simultaneously output from the INTR pin.

Question 6 : What will happen if non-existent time is set?

Answer 6: Time or alarm digits which are non-existent or indicated in non-BCD notation can be set in the

time counter or the alarm register without causing any trouble. If such invalid digits are left,

however, they may cause faulty time count operation in case of a carry or mismatching between

clock time and alarm time.

Question 7 : How can an alarm interrupt be used in battery backup? (Why is an alarm interrupt not out-

put in battery backup?)

Answer 7: An alarm interrupt is normally output from the INTR pin in battery backup (while the CE pin is

held low). Its output is most likely to fail, therefore, when the other end of the pull-up resistor

of the INTR pin is connected to any power supply which may be turned off. To prevent this

problem, confirm that the other end of the pull-up resistor of the INTR pin is connected to the

backup battery.

Question 8 : How can an alarm interrupt be output on a monthly basis?

Answer 8: The RP/RF/RS5C62 are configured to issue a daily alarm and cannot be reconfigured to gener-

ate an alarm interrupt on a monthly basis. Considering that they are designed to reduce cur-

rent consumption as described in “Note” below, an advisable alternative action is to generate an

alarm interrupt to the CPU on a daily basis and keep track of alarm dates in a software-con-

trolled process.

Note

: The RP/RF/RS5C62 are designed to reduce current consumption (ensure typical current con-

sumption on the order of 1µA for 3V). Daily current consumption can be calculated as follows :

Assuming, for example, that an alarm interrupt to the CPU is generated on a daily basis as the

CPU is operating for a period of 0.5seconds with peak current consumption of 20mA, daily cur-

rent consumption can be calculated from the equation : 0.5s´20mA/60 ´60´24 = 0.115µA. This

means a total base current of a little more than 1µA, a slight increase in current consumption.

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