25.5.10 Client Control B

Name: SCTRLB
Offset: 0x0A
Reset: 0x00
Property: -

Bit 76543210 
      ACKACTSCMD[1:0] 
Access R/WR/WR/W 
Reset 000 

Bit 2 – ACKACT 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.

ValueNameDescription
0ACKSend ACK
1NACKSend NACK

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 25-3. Command Settings
ValueNameDIRDescription
0x0NOACTXNo action
0x1XReserved
0x2COMPTRANSWExecute Acknowledge Action succeeded by waiting for any Start (S/Sr) conditionUsed to complete a transaction
RWait for any Start (S/Sr) condition
0x3RESPONSEWExecute Acknowledge Action succeeded by reception of next byte
RUsed 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.