ATMEGA640 datasheet(258/436 Pages) MICROCHIP

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258

ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

Figure 24-18. Formats and States in the Slave Transmitter Mode

24.7.5

Miscellaneous States

There are two status codes that do not correspond to a defined TWI state, see Table 24-6 on page 259.

Status 0xF8 indicates that no relevant information is available because the TWINT Flag is not set. This occurs

between other states, and when the TWI is not involved in a serial transfer.

Status 0x00 indicates that a bus error has occurred during a 2-wire Serial Bus transfer. A bus error occurs when a

START or STOP condition occurs at an illegal position in the format frame. Examples of such illegal positions are

during the serial transfer of an address byte, a data byte, or an acknowledge bit. When a bus error occurs, TWINT

is set. To recover from a bus error, the TWSTO Flag must set and TWINT must be cleared by writing a logic one to

0xB8

Data byte in TWDR has been

transmitted; ACK has been re-

ceived

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 re-

ceived

0xC0

Data byte in TWDR has been

transmitted; NOT ACK has been

received

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

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

Table 24-5.

Status Codes for Slave Transmitter Mode (Continued)

SLA

DATA

$A8

$B8

$B0

Reception of the own

slave address and one or

more data bytes

Last data byte transmitted.

Switched to not addressed

slave (TWEA = '0')

Arbitration lost as master

and addressed as slave

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

P or S

DATA

$C0

DATA

$C8

P or S

All 1's

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