R2023K datasheet(28/50 Pages) RICOH

28 / 50 page

R2023K/T

• Data Transmission under Special Condition

The R2023K/T 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. 61

µs from Stop

Condition.

To prevent invalid read or write, clock and calendar data 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 R2023K/T 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

2C-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

R2023K/T 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.

No Stop Condition shall be generated until clock and calendar data read/write is started and completed.

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

Do not make Start Condition within 61

µs from Stop Condition. When clock is carried during the access, which will

be adjusted within approx. 61

µs 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 R2023K/T 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.

R2023K 데이터시트(PDF) 28 Page - RICOH electronics devices division