Starting And Stopping I C Bus Communications - Epson RA8804 CE Applications Manual

RA8804 CE
8.10.3. Starting and stopping I
START
condition
SCL
[ S ]
SDA
1) START condition, repeated START condition, and STOP condition
(1) START condition

The SDA level changes from high to low while SCL is at high level.
(2) STOP condition
This condition regulates how communications on the I 2 C-BUS are terminated. The SDA level

changes from low to high while SCL is at high level.
(3) Repeated START condition (RESTART condition)

In some cases, the START condition occurs between a previous START condition and the next
STOP condition, in which case the second START condition is distinguished as a RESTART
condition. Since the required status is the same as for the START condition, the SDA level
changes from high to low while SCL is at high level.
2) Caution points
1) The master device always controls the START, RESTART, and STOP conditions for communications.
2) The master device does not impose any restrictions on the timing by which STOP conditions affect
transmissions, so communications can be forcibly stopped at any time while in progress. (However, this
is only when this RTC module is in receiver mode (data reception mode = SDA released).
3) When communicating with this RTC module, the series of operations from transmitting the START
condition to transmitting the STOP condition should occur within 1 seconds. (A RESTART condition
may be sent between a START condition and STOP condition, but even in such cases the series of
operations from transmitting the START condition to transmitting the STOP condition should still occur
within 1 second.)
If this series of operations requires 1 seconds or longer, the I
cleared and set to standby mode by this RTC module's bus timeout function. Note with caution that both
write and read operations are invalid for communications that occur during or after this auto clearing
operation. (When the read operation is invalid, all data that is read has a value of "1").
Restarting of communications begins with transfer of the START condition again
4) When communicating with this RTC module, wait at least 1.3 μs (see the tBUF rule) between
transferring a STOP condition (to stop communications) and transferring the next START condition (to
start the next round of communications).
SCL
SDA
2
C bus communications
Repeated START(RESTART)
condition
[ Sr ]
1s ( Max. )
STOP
condition
[ P ]
1.3s (Min.)
2
C bus interface will be automatically
START
condition
[ S ]
Page - 32
STOP
condition
[ P ]
ETM60E-02