CHAPTER 5. PERIPHERAL HARDWARE FUNCTIONS

After the slave receives the data length, if the area for storing the receive data is at least as large as that data length, the slave returns ACK. If the data storage area is too small, ACK is not returned and an error is generated.

When all the data has been transferred, the master sends an END command. This command notifies the slave that all the data has been correctly transferred.

The slave may also receive an END command before the reception of all the data. In this case, the data up to the reception of the END command is valid.

When data is transmitted, the master compares the SIO contents before and after the transmission to check whether the data was correctly output onto the bus. If the SIO contents before and after the transmission are different, the master suspends data transmission by sending a STOP command.

Fig. 5-56 STOP Command Transfer Format

MSM

 

 

 

 

 

 

 

 

 

Data

 

 

ACK

 

 

STOP

 

 

 

 

 

 

 

 

 

 

Data

 

 

 

 

 

Command

 

 

 

 

 

 

 

 

 

Data Check

 

 

 

Error Generation

Remarks M : Output by master

S : Output by slave

S

ACK

Data Transfer Suspended

When the slave receives a STOP command, the byte of data received immediately before the command is invalid.

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NEC PD75402A, PD75P402 user manual 122, Msm, ACK Stop