ATMEGA8-16AI SL383 Atmel, ATMEGA8-16AI SL383 Datasheet - Page 179

• Manufacturer Part Number: ATMEGA8-16AI SL383
• Description: Semiconductors and Actives, Microprocessors, Microcontrollers
• Manufacturer: Atmel

Master Transmitter
Mode
2486W–AVR–02/10
In the Master Transmitter mode, a number of data bytes are transmitted to a Slave Receiver
(see
format of the following address packet determines whether Master Transmitter or Master
Receiver mode is to be entered. If SLA+W is transmitted, MT mode is entered, if SLA+R is trans-
mitted, MR mode is entered. All the status codes mentioned in this section assume that the
prescaler bits are zero or are masked to zero.
Figure 78. Data Transfer in Master Transmitter Mode
A START condition is sent by writing the following value to TWCR:
TWEN must be set to enable the Two-wire Serial Interface, TWSTA must be written to one to
transmit a START condition and TWINT must be written to one to clear the TWINT Flag. The
TWI will then test the Two-wire Serial Bus and generate a START condition as soon as the bus
becomes free. After a START condition has been transmitted, the TWINT Flag is set by hard-
ware, and the status code in TWSR will be 0x08 (see
SLA+W must be transmitted. This is done by writing SLA+W to TWDR. Thereafter the TWINT bit
should be cleared (by writing it to one) to continue the transfer. This is accomplished by writing
the following value to TWCR:
When SLA+W have been transmitted and an acknowledgement bit has been received, TWINT is
set again and a number of status codes in TWSR are possible. Possible status codes in Master
mode are 0x18, 0x20, or 0x38. The appropriate action to be taken for each of these status codes
is detailed in
When SLA+W has been successfully transmitted, a data packet should be transmitted. This is
done by writing the data byte to TWDR. TWDR must only be written when TWINT is high. If not,
the access will be discarded, and the Write Collision bit (TWWC) will be set in the TWCR Regis-
ter. After updating TWDR, the TWINT bit should be cleared (by writing it to one) to continue the
transfer. This is accomplished by writing the following value to TWCR:
TWCR
value
TWCR
value
TWCR
value
Figure
SDA
SCL
78). In order to enter a Master mode, a START condition must be transmitted. The
TWINT
TWINT
TWINT
Table
1
1
1
66.
TRANSMITTER
Device 1
MASTER
TWEA
TWEA
TWEA
X
X
X
Device 2
TWSTA
TWSTA
TWSTA
RECEIVER
SLAVE
1
0
0
TWSTO
TWSTO
TWSTO
Device 3
0
0
0
........
TWWC
TWWC
TWWC
X
X
X
Table
Device n
TWEN
TWEN
TWEN
66). In order to enter MT mode,
V
1
1
1
CC
R1
ATmega8(L)
–
0
–
0
–
0
R2
TWIE
TWIE
TWIE
X
X
X
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