Toshiba TMP91C815F Data Book page 164

(8)
When a serial bus interface interrupt request (INTS2) occurs, the SBI0CR2 <PIN> is cleared to
"0". During the time that the SBI0CR2<PIN> is "0", the SCL line is pulled down to the Low level.
The <PIN> is cleared to "0" when a 1-word of data is transmitted or received. Either writing /
reading data to / from SBI0DBR sets the <PIN> to "1".
The time from the <PIN> being set to "1" until the SCL line is released takes t
In the address recognition mode (<ALS> = 0), <PIN> is cleared to "0" when the received slave
address is the same as the value set at the I2C0AR or when a GENERAL CALL is received (all 8-bit
data are "0" after a start condition). Although SBI0CR2<PIN> can be set to "1" by the program, the
<PIN> is not clear it to "0" when it is written "0".
(9) Serial bus interface operation mode selection
SBI0CR2<SBIM1 to SBIM0> is used to specify the serial bus interface operation mode. Set
SBI0CR2<SBIM1 to SBIM0> to "10" when the device is to be used in I
Switch a mode to port after confirming a bus is free.
(10) Arbitration lost detection monitor
Since more than one master device can exist simultaneously on the bus in I
arbitration procedure has been implemented in order to guarantee the integrity of transferred data.
Data on the SDA line is used for I
The following shows an example of a bus arbitration procedure when two master devices exist
simultaneously on the bus. Master A and Master B output the same data until point "a". After
Master A outputs "L" and Master B, "H", the SDA line of the bus is wire-AND and the SDA line is
pulled down to the Low-level by Master A. When the SCL line of the bus is pulled up at point b, the
slave device reads the data on the SDA line, that is, data in Master A. A data transmitted from
Master B becomes invalid. The state in Master B is called "ARBITRATION LOST". Master B
device which loses arbitration releases the internal SDA output in order not to affect data
transmitted from other masters with arbitration. When more than one master sends the same data at
the first word, arbitration occurs continuously after the second word.
SCL line
Internal SDA output
(Master A)
Internal SDA output
(Master A)
SDA line
Interrupt service requests and interrupt cancellation
2
C bus arbitration.
a b
Figure 3.10.11 Arbitration Lost
91C815-
Internal SDA output becomes 1 after arbitration has been lost.
161
TMP91C815
.
LOW
2
C Bus Mode.
2
C Bus Mode, a bus