27.5.10 Slave 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

This bit defines the slave’s behavior under certain conditions defined by the bus protocol state and software interaction. The table below lists the acknowledge procedure performed by the slave if action is initiated by software. The acknowledge action is performed when TWIn.SDATA is read or written, or when an execute command is written to the CMD bits in this register.

The ACKACT bit is not a flag or strobe, but an ordinary read/write accessible register bit.

ValueNameDescription
0 ACK Send ACK
1 NACK Send NACK

Bits 1:0 – SCMD[1:0] Command

Unlike the acknowledge action bits, the Slave command bits are strobes. These bits always read as '0'. Writing to these bits trigger a slave operation as defined in the table below.

Table 27-5. Command Settings
SCMD[1:0] DIR Description
0x0 X NOACT - No action
0x1 X Reserved
0x2 - COMPTRANS Used to complete a transaction.
0 Execute Acknowledge Action succeeded by waiting for any Start (S/Sr) condition.
1 Wait for any Start (S/Sr) condition.
0x3 - RESPONSE Used in response to an address interrupt (APIF).
0 Execute Acknowledge Action succeeded by reception of next byte.
1 Execute Acknowledge Action succeeded by slave data interrupt.
Used in response to a data interrupt (DIF).
0 Execute Acknowledge Action succeeded by reception of next byte.
1 Execute a byte read operation followed by Acknowledge Action.

The acknowledge action bits and command bits can be written at the same time.