AT89LP6440 datasheet(111/194 Pages) ATMEL

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3706A–MICRO–9/09

AT89LP6440 - Preliminary

18.4

Table 18-1.

TWCR – Two-Wire Control Register

TWCR Address = AAH

Reset Value = X000 00XXB

Not Bit Addressable

–TWEN

STA

STO

TWIF

–

Bit

76543

210

Symbol

Function

TWEN

Two-wire Serial Interface Enable. Set to enable the TWI. Clear to disable the TWI.

STA

Start Flag. Set to send a START condition on the bus. Must be cleared by software.

STO

Stop Flag. Set to send a STOP condition on the bus. Cleared automatically by hardware when the STOP occurs.

TWIF

Two-wire Interface Interrupt Flag. Set by hardware when the TWI requests an interrupt. TWIF must be cleared by

software. While TWIF is set, the SCL low period is stretched. Note that clearing this flag starts the operation of the TWI,

so all accesses to the other TWI registers (TWAR, TWSR and TWDR) must be complete before clearing this flag.

Assert Acknowledge Flag. Clear in master and slave receiver modes, to force a not acknowledge (high level on SDA).

Clear to disable SLA or GCA recognition. Set to recognize SLA or GCA (if GC set) for entering slave receiver or

transmitter modes. Set in master and slave receiver modes, to force an acknowledge (low level on SDA). This bit has no

effect when in master transmitter mode. By clearing AA to zero, the device can be virtually disconnected from the Two-

wire Serial Bus temporarily. Address recognition can then be resumed by setting the AA bit to one again.

Table 18-2.

TWSR – Two-Wire Status Register

TWSR Address = ABH

Reset Value = 1111 1000B

Not Bit Addressable

TWS7TWS6TWS5TWS4TWS3

000

Bit

76543

210

Symbol

Function

TWS

7-0

Two-wire Interface Status. The current status code of the TWI logic and serial bus. See Table 18-6 through Table 18-10

for a description of the status codes. Note that the three least significant bits always read as zero. The Status code is

valid only while TWIF remains set.

Table 18-3.

TWAR – Two-Wire Address Register

TWAR Address = ACH

Reset Value = 1111 1110B

Not Bit Addressable

TWA6

TWA5

TWA4

TWA3

TWA2

TWA1

TWA0

Bit

76543

210

Symbol

Function

TWA6-0

Two-wire Interface Slave Address. The TWI will only respond to slave addresses that match this 7-bit address.

General Call Enable. Set to enable General Call address (00h) recognition. Clear to disable General Call address

recognition.

AT89LP6440 Datasheet(PDF) 111 Page - ATMEL Corporation

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