AT90CAN32_14 Datasheet, PDF (224/428 Pages) ATMEL Corporation – High-performance, Low-power AVR 8-bit Microcontroller

Table 18-4. Status Codes for Master Receiver Mode
Status Code
(TWSR)
Prescaler Bits
are 0
0x08
0x10
Status of the Two-wire Serial Bus
Application Software Response
and Two-wire Serial Interface
To TWCR
Hardware
To/from TWDR
STA
STO TWINT
A START condition has been Load SLA+R
X
transmitted
0
1
A repeated START condition has Load SLA+R or
X
been transmitted
Load SLA+W
X
0
1
0
1
0x38
Arbitration lost in SLA+R or NOT No TWDR action or 0
ACK bit
No TWDR action
1
0
1
0
1
0x40
SLA+R has been transmitted;
ACK has been received
No TWDR action or 0
No TWDR action
0
0
1
0
1
Next Action Taken by TWI Hardware
TWEA
X SLA+R will be transmitted
ACK or NOT ACK will be received
X SLA+R will be transmitted
ACK or NOT ACK will be received
X SLA+W will be transmitted
Logic will switch to master transmitter mode
X Two-wire Serial Bus will be released and not addressed
slave mode will be entered
X A START condition will be transmitted when the bus
becomes free
0 Data byte will be received and NOT ACK will be
returned
1 Data byte will be received and ACK will be returned
0x48
0x50
0x58
SLA+R has been transmitted;
NOT ACK has been received
Data byte has been received;
ACK has been returned
Data byte has been received;
NOT ACK has been returned
No TWDR action or 1
No TWDR action or 0
No TWDR action
1
Read data byte or 0
Read data byte
0
Read data byte or 1
Read data byte or 0
Read data byte
1
0
1
1
1
1
1
0
0
0
1
1
1
1
1
1
1
X
X
X
0
1
X
X
X
Repeated START will be transmitted
STOP condition will be transmitted and TWSTO flag will
be reset
STOP condition followed by a START condition will be
transmitted and TWSTO flag will be reset
Data byte will be received and NOT ACK will be
returned
Data byte will be received and ACK will be returned
Repeated START will be transmitted
STOP condition will be transmitted and TWSTO flag will
be reset
STOP condition followed by a START condition will be
transmitted and TWSTO flag will be reset
18.8.3
Slave Receiver Mode
In the Slave Receiver mode, a number of data bytes are received from a master transmitter (see
Figure 18-15). All the status codes mentioned in this section assume that the prescaler bits are
zero or are masked to zero.
Figure 18-15. Data Transfer in Slave Receiver Mode
Device 1
SLAVE
RECEIVER
Device 2
MASTER
TRANSMITTER
SDA
SCL
Device 3 ........ Device n
V_CC
R1
R2
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