Client Control B

  0x0A 8 - 0x00    

Client Control B

Bit  7 6 5 4 3 2 1 0  
            ACKACT SCMD[1:0]  
Access            R/W R/W R/W  
Reset            0 0 0  

Bit 2 – ACKACT: Acknowledge Action

Acknowledge Action

The ACKACT(1) bit represents the behavior of the client device under certain conditions defined by the bus protocol state and the software interaction. If the Smart Mode Enable (SMEN) bit in the Client Control A (TWIn.SCTRLA) register is set to ‘1’, the acknowledge action is performed when the Client Data (TWIn.SDATA) register is read, else a command must be written to the Command (SCMD) bit field in the Client Control B (TWIn.SCTRLB) register.

The acknowledge action is not performed when the Client Data (TWIn.SDATA) register is written since the client is sending data.

0 ACK Send ACK

Bits 1:0 – SCMD[1:0]: Command


The SCMD(1) bit field is a strobe. This bit field is always read as ‘0’.

Writing to this bit field triggers a client operation as defined by the table below.

Table 1. Command Settings
Value Name DIR Description
0x0 NOACT X No action
0x1 X Reserved
0x2 COMPTRANS W Execute Acknowledge Action succeeded by waiting for any Start (S/Sr) condition Used to complete a transaction
R Wait for any Start (S/Sr) condition
0x3 RESPONSE W Execute Acknowledge Action succeeded by reception of next byte
R Used in response to an address interrupt (APIF): Execute Acknowledge Action succeeded by client data interrupt.
Used in response to a data interrupt (DIF): Execute a byte read operation followed by Acknowledge Action.
Note: 1. The ACKACT bit and the SCMD bit field can be written at the same time. The ACKACT will be updated before the command is triggered.