The 14 registers of TWI0 (Two-Wire Interface), from 0x900, with their reset value and every field. The AVR16DU20 has 408 registers in 39 peripherals, one page each.
TWI0 Two-Wire Interface
CTRLAControl A
Address
0x900
Reset
0x00
Access
read/write
7–
6INPUTLVL
5–
4SDASETUP
3SDAHOLD1
2SDAHOLD0
1FMPEN
0–
4 fields
Field
Bits
What it does
INPUTLVL
6
Input voltage transition level
0 I2C input voltage transition level
1 SMBus 3.0 input voltage transition level
SDASETUP
4
SDA Setup Time
0 SDA setup time is four clock cycles
1 SDA setup time is eight clock cycle
SDAHOLD
3:2
SDA Hold Time
0 No SDA Hold Delay
1 Short SDA hold time
2 Meets SMBUS 2.0 specification under typical conditions
3 Meets SMBUS 2.0 specificaiton across all corners
FMPEN
1
Fast-mode Plus Enable
0 Operating in Standard-mode or Fast-mode
1 Operating in Fast-mode Plus
DBGCTRLDebug Control
Address
0x902
Reset
0x00
Access
read/write
7–
6–
5–
4–
3–
2–
1–
0DBGRUN
1 field
Field
Bits
What it does
DBGRUN
0
Debug Run
0 The peripheral is halted in Break Debug mode and ignores events
1 The peripheral will continue to run in Break Debug mode when the CPU is halted
MCTRLAHost Control A
Address
0x903
Reset
0x00
Access
read/write
7RIEN
6WIEN
5–
4QCEN
3TIMEOUT1
2TIMEOUT0
1SMEN
0ENABLE
6 fields
Field
Bits
What it does
RIEN
7
Read Interrupt Enable
WIEN
6
Write Interrupt Enable
QCEN
4
Quick Command Enable
TIMEOUT
3:2
Inactive Bus Time-Out
0 Bus time-out disabled. I2C.
1 50us - SMBus
2 100us
3 200us
SMEN
1
Smart Mode Enable
ENABLE
0
Enable
MCTRLBHost Control B
Address
0x904
Reset
0x00
Access
read/write
7–
6–
5–
4–
3FLUSH
2ACKACT
1MCMD1
0MCMD0
3 fields
Field
Bits
What it does
FLUSH
3
Flush
ACKACT
2
Acknowledge Action
0 Send ACK
1 Send NACK
MCMD
1:0
Command
0 No action
1 Execute Acknowledge Action followed by repeated Start.
2 Execute Acknowledge Action followed by a byte read/write operation. Read/write is defined by DIR.
3 Execute Acknowledge Action followed by issuing a Stop condition.
MSTATUSHost STATUS
Address
0x905
Reset
0x00
Access
read/write
7RIF
6WIF
5CLKHOLD
4RXACK
3ARBLOST
2BUSERR
1BUSSTATE1
0BUSSTATE0
7 fields
Field
Bits
What it does
RIF
7
Read Interrupt Flag
WIF
6
Write Interrupt Flag
CLKHOLD
5
Clock Hold
RXACK
4
Received Acknowledge
ARBLOST
3
Arbitration Lost
BUSERR
2
Bus Error
BUSSTATE
1:0
Bus State
0 Unknown bus state
1 Bus is idle
2 This TWI controls the bus
3 The bus is busy
MBAUDHost Baud Rate
Address
0x906
Reset
0x00
Access
read/write
7BAUD7
6BAUD6
5BAUD5
4BAUD4
3BAUD3
2BAUD2
1BAUD1
0BAUD0
1 field
Field
Bits
What it does
BAUD
7:0
Baud Rate
MADDRHost Address
Address
0x907
Reset
0x00
Access
read/write
7ADDR7
6ADDR6
5ADDR5
4ADDR4
3ADDR3
2ADDR2
1ADDR1
0ADDR0
1 field
Field
Bits
What it does
ADDR
7:0
Address
MDATAHost Data
Address
0x908
Reset
0x00
Access
read/write
7DATA7
6DATA6
5DATA5
4DATA4
3DATA3
2DATA2
1DATA1
0DATA0
1 field
Field
Bits
What it does
DATA
7:0
Data
SCTRLAClient Control A
Address
0x909
Reset
0x00
Access
read/write
7DIEN
6APIEN
5PIEN
4–
3–
2PMEN
1SMEN
0ENABLE
6 fields
Field
Bits
What it does
DIEN
7
Data Interrupt Enable
APIEN
6
Address or Stop Interrupt Enable
PIEN
5
Stop Interrupt Enable
PMEN
2
Address Recognition Mode
SMEN
1
Smart Mode Enable
ENABLE
0
Enable
SCTRLBClient Control B
Address
0x90A
Reset
0x00
Access
read/write
7–
6–
5–
4–
3–
2ACKACT
1SCMD1
0SCMD0
2 fields
Field
Bits
What it does
ACKACT
2
Acknowledge Action
0 Send ACK
1 Send NACK
SCMD
1:0
Command
0 No Action
2 Complete transaction
3 Used in response to an interrupt
SSTATUSClient Status
Address
0x90B
Reset
0x00
Access
read/write
7DIF
6APIF
5CLKHOLD
4RXACK
3COLL
2BUSERR
1DIR
0AP
8 fields
Field
Bits
What it does
DIF
7
Data Interrupt Flag
APIF
6
Address or Stop Interrupt Flag
CLKHOLD
5
Clock Hold
RXACK
4
Received Acknowledge
COLL
3
Collision
BUSERR
2
Bus Error
DIR
1
Read/Write Direction
AP
0
Address or Stop
0 A Stop condition generated the interrupt on APIF flag
1 Address detection generated the interrupt on APIF flag
BETA