Slave Control B

Name:
SCTRLB
Offset:
0x0A
Reset:
0x00
Access:
-
Bit76543210
ACKACTSCMD[1:0]
AccessR/WR/WR/W
Reset000

Bit 2 – ACKACT: Acknowledge Action

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

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 1. 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.