RV5C386A-E2 Просмотр технического описания (PDF) - RICOH Co.,Ltd.

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RV5C386A-E2

I2C-Bus Real-Time Clock ICs with Voltage Monitoring Function

RICOH Co.,Ltd. 

PRELIMINARY

RV5C386A

14.1.5. Data Transmission under Special Condition

The RV5C386A holds the clock tentatively for duration from Start Condition to avoid invalid read or write

clock on carrying clock. When clock carried during this period, which will be adjusted within approx. 61µs

from Stop Condition. To prevent invalid read or write, clock shall be made during one transmission

operation (from Start Condition to Stop Condition). When 0.5 to 1.0 second elapses after Start Condition,

any access to the RV5C386A is automatically released to release tentative hold of the clock, and access from

the CPU is forced to be terminated (The same action as made Stop Condition is received: automatic resume

function from I2C-Bus interface). Therefore, one access must be complete within 0.5 seconds. The

automatic resume function prevents delay in clock even if SCL is stopped from sudden failure of the system

during clock read operation.

Also a second Start Condition after the first Start Condition and before the Stop Condition is regarded

“Repeated Start Condition”. Therefore, when 0.5 to 1.0 seconds passed after the first Start Condition, an

access to the RV5C386A is automatically released.

If access is tried after automatic resume function is activated, no acknowledge signal will be output for writing

while FFh will be output for reading.

The user shall always be able to access the real-time clock as long as three conditions are met.

(1) No Stop Condition shall be generated until clock read/write is started and completed.

(2) One cycle read/write operation shall be complete within 0.5 seconds.

(3) Do not make Start Condition within 61µs from Stop Condition. When clock is carried during the access,

which will be adjusted within approx. 61µs from Stop Condition.

Bad example of reading from seconds to hours (invalid read)

(Start Condition) → (Read of seconds) → (read of minutes) → (Stop Condition) → (Start Condition) → (Read

of hour) → (Stop Condition)

Assuming read was started at 05:59:59 P.M. and while reading seconds and minutes the time advanced to

06:00:00 P.M. At this time second digit is hold so read the read as 05:59:59. Then the RV5C386A confirms

(Stop Condition) and carries second digit being hold and the time change to 06:00:00 P.M. Then, when the

hour digit is read, it changes to 6. The wrong results of 06:59:59 will be read.

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