TMP86FS49AIUG datasheet(225/296 Pages) TOSHIBA

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Page 209

TMP86FS49AIUG

Figure 16-13 Stop Condition Generation

16.6.5 Restart

Restart is used to change the direction of data transfer between a master device and a slave device during

transferring data. The following explains how to restart a serial bus interface circuit.

Clear “0” to the MST, TRX and BB and set “1” to the PIN. The SDA pin retains the high-level and the SCL

pin is released. Since a stop condition is not generated on a bus, a bus is assumed to be in a busy state from

other devices. Test the BB until it becomes “0” to check that the SCL pin of a serial bus interface circuit is

released. Test the LRB until it becomes “1” to check that the SCL line on a bus is not pulled-down to the low

level by other devices. After confirming that a bus stays in a free state, generate a start condition with proce-

dure " 16.6.2 Start condition and slave address generation ".

In order to meet setup time when restarting, take at least 4.7

µs of waiting time by software from the time of

restarting to confirm that a bus is free until the time to generate a start condition.

Note:When the master is in the receiver mode, it is necessary to stop the data transmission from the slave devcie

before the STOP condtion is generated. To stop the transmission, the master device make the slave device

receiving a negative acknowledge. Therefore, the LRB is "1" before generating the Restart and it can not be

confirmed that SCL line is not pulled-down by other devices. Please confirm the SCL line state by reading the

port.

Figure 16-14 Timing Diagram when Restarting

"1"

MST

"1"

TRX

"0"

"1"

BB (Read)

Stop condition

SCL pin

SDA pin

SCL (Bus)

"0"

MST

"0"

TRX

"0"

"1"

LRB

Start condition

"1"

MST

"1"

TRX

"1"

4.7

µs (Min)

SCL pin

SDA pin

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