Table 25-6, Table 25-6 on, Atmega128rfa1 – Rainbow Electronics ATmega128RFA1 User Manual

Page 398

398

8266A-MCU Wireless-12/09

ATmega128RFA1

will then wake up from sleep and the TWI will hold the SCL clock will low during the
wake up and until the TWINT Flag is cleared (by writing it to one). Further data
transmission will be carried out as normal, with the AVR clocks running as normal.
Observe that if the AVR is set up with a long start-up time, the SCL line may be held
low for a long time, blocking other data transmissions.

Note that the 2-wire Serial Interface Data Register – TWDR does not reflect the last
byte present on the bus when waking up from these sleep modes.

Table 25-6. Status Code for Slave Transmitter Mode

Application Software Response

To TWCR

Status Code

(TWSR)

Prescaler
Bits are 0

Status of the 2-wire

Serial Bus and 2-wire

Serial Interface

Hardware

To/from TWDR

STA

STD

TWINT

TWEA

Next Action Taken by TWI
Hardware

0xA8

Own SLA+R has been
received; ACK has been
returned

Load data byte or

Load data byte

Last data byte will be transmitted and
NOT ACK should be received Data
byte will be transmitted and ACK
should be received

0xB0

Arbitration lost in SLA+R/W
as Master; own SLA+R has
been received; ACK has
been returned

Load data byte or

Load data byte

Last data byte will be transmitted and
NOT ACK should be received Data
byte will be transmitted and ACK
should be received

0xB8

Data byte in TWDR has
been transmitted; ACK has
been received

Load data byte or

Load data byte

Last data byte will be transmitted and
NOT ACK should be received
Data byte will be transmitted and
ACK should be received

0xC0

Data byte in TWDR has
been transmitted; NOT
ACK has been received

No TWDR action or

No TWDR action or

No TWDR action or

No TWDR action

Switched to the not addressed Slave
mode; no recognition of own SLA or
GCA
Switched to the not addressed Slave
mode; own SLA will be recognized;
GCA will be recognized if TWGCE =
“1”
Switched to the not addressed Slave
mode; no recognition of own SLA or
GCA; a START condition will be
transmitted when the bus becomes
free
Switched to the not addressed Slave
mode; own SLA will be recognized;
GCA will be recognized if TWGCE =
“1”; a START condition will be
transmitted when the bus becomes
free

0xC8

Last data byte in TWDR
has been transmitted
(TWEA = “0”); ACK has
been received

No TWDR action or

No TWDR action or

No TWDR action or

No TWDR action