Rainbow Electronics ATmega128RFA1 - Manual (Page 389)

389
8266A-MCU Wireless-12/09
ATmega128RFA1
TWCR
TWINT TWEA TWSTA TWSTO TWWC TWEN – TWIE
Value
1 X 0 0 X 1 0 X
This scheme is repeated until the last byte has been sent and the transfer is ended by
generating a STOP condition or a repeated START condition. A STOP condition is
generated by writing the following value to TWCR:
TWCR
TWINT TWEA TWSTA TWSTO TWWC TWEN – TWIE
Value
1 X 0 1 X 1 0 X
A REPEATED START condition is generated by writing the following value to TWCR:
TWCR
TWINT TWEA TWSTA TWSTO TWWC TWEN – TWIE
Value
X 1 0 X 1 0 X
After a REPEATED START condition (state 0x10) the 2-wire Serial Interface can
access the same Slave again, or a new Slave without transmitting a STOP condition.
Repeated START enables the Master to switch between Slaves, Master Transmitter
mode and Master Receiver mode without losing control of the bus.
Figure 25-12. Formats and States in the Master Transmitter Mode
S SLA W A DATA A P
$08 $18 $28
R SLA W
$10
A P
$20
P
$30
A or A
$38
A
Other master
continues
A or A
$38
Other master
continues
R
A
$68
Other master
continues
$78 $B0
To corresponding
states in slave mode
MT
MR
Successfull
transmission
to a slave
receiver
Next transfer
started with a
repeated start
condition
Not acknowledge
received after the
slave address
Not acknowledge
received after a data
byte
Arbitration lost in slave
address or data byte
Arbitration lost and
addressed as slave
DATA A
n
From master to slave
From slave to master
Any number of data bytes
and their associated acknowledge bits
This number (contained in TWSR) corresponds
to a defined state of the Two-Wire Serial Bus. The
prescaler bits are zero or masked to zero
S