MEGA128CAN Datasheet, PDF (220/413 Pages) ATMEL Corporation – Microcontroller WITH 128K BYTES OF ISP FLASH AND CAN CONTROLLER

Table 91. Status Codes for Master Receiver Mode
Status Code
(TWSR)
Prescaler Bits
are 0
0x08
0x10
Status of the Two-wire Serial
Bus and Two-wire Serial Inter-
face Hardware
A START condition has been
transmitted
A repeated START condition
has been transmitted
Application Software Response
To/from TWDR
To TWCR
STA
STO
Load SLA+R
X
0
Load SLA+R or
X
0
Load SLA+W
X
0
0x38
Arbitration lost in SLA+R or NOT No TWDR action or 0
0
ACK bit
No TWDR action
1
0
0x40
SLA+R has been transmitted; No TWDR action or 0
0
ACK has been received
No TWDR action
0
0
TWINT
1
1
1
1
1
1
1
TWEA
X
X
X
X
X
0
1
Next Action Taken by TWI Hardware
SLA+R will be transmitted
ACK or NOT ACK will be received
SLA+R will be transmitted
ACK or NOT ACK will be received
SLA+W will be transmitted
Logic will switch to master transmitter mode
Two-wire Serial Bus will be released and not addressed
slave mode will be entered
A START condition will be transmitted when the bus
becomes free
Data byte will be received and NOT ACK will be
returned
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
1
0
1
0
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
Slave Receiver Mode
In the Slave Receiver mode, a number of data bytes are received from a master trans-
mitter (see Figure 104). All the status codes mentioned in this section assume that the
prescaler bits are zero or are masked to zero.
Figure 104. Data Transfer in Slave Receiver Mode
Device 1
SLAVE
RECEIVER
Device 2
MASTER
TRANSMITTER
Device 3 ........ Device n
V_CC
R1
R2
SDA
SCL
To initiate the Slave Receiver mode, TWAR and TWCR must be initialized as follows:
TWAR
value
TWA6
TWA5
TWA4
TWA3
TWA2
Device’s Own Slave Address
TWA1
TWA0
TWGCE
220 AT90CAN128
4250E–CAN–12/04