AT90SCR100 datasheet(306/433 Pages) ATMEL

306 / 433 page

306

TPR0327AY–SMS–30Jan09

AT90SCR100

the application has cleared TWINT, the TWI will initiate transmission of the START

condition.

2. When the START condition has been transmitted, the TWINT Flag in TWCR is set, and

TWSR is updated with a status code indicating that the START condition has success-

fully been sent.

3. The application software should now examine the value of TWSR, to make sure that

the START condition was successfully transmitted. If TWSR indicates otherwise, the

application software might take some special action, like calling an error routine.

Assuming that the status code is as expected, the application must load SLA+W into

TWDR. Remember that TWDR is used both for address and data. After TWDR has

been loaded with the desired SLA+W, a specific value must be written to TWCR,

instructing the TWI hardware to transmit the SLA+W present in TWDR. Which value to

write is described later on. However, it is important that the TWINT bit is set in the value

written. Writing a one to TWINT clears the flag. The TWI will not start any operation as

long as the TWINT bit in TWCR is set. Immediately after the application has cleared

TWINT, the TWI will initiate transmission of the address packet.

4. When the address packet has been transmitted, the TWINT Flag in TWCR is set, and

TWSR is updated with a status code indicating that the address packet has success-

fully been sent. The status code will also reflect whether a Slave acknowledged the

packet or not.

5. The application software should now examine the value of TWSR, to make sure that

the address packet was successfully transmitted, and that the value of the ACK bit was

as expected. If TWSR indicates otherwise, the application software might take some

special action, like calling an error routine. Assuming that the status code is as

expected, the application must load a data packet into TWDR. Subsequently, a specific

value must be written to TWCR, instructing the TWI hardware to transmit the data

packet present in TWDR. Which value to write is described later on. However, it is

important that the TWINT bit is set in the value written. Writing a one to TWINT clears

the flag. The TWI will not start any operation as long as the TWINT bit in TWCR is set.

Immediately after the application has cleared TWINT, the TWI will initiate transmission

of the data packet.

6. When the data packet has been transmitted, the TWINT Flag in TWCR is set, and

TWSR is updated with a status code indicating that the data packet has successfully

been sent. The status code will also reflect whether a Slave acknowledged the packet

or not.

7. The application software should now examine the value of TWSR, to make sure that

the data packet was successfully transmitted, and that the value of the ACK bit was as

expected. If TWSR indicates otherwise, the application software might take some spe-

cial action, like calling an error routine. Assuming that the status code is as expected,

the application must write a specific value to TWCR, instructing the TWI hardware to

transmit a STOP condition. Which value to write is described later on. However, it is

important that the TWINT bit is set in the value written. Writing a one to TWINT clears

the flag. The TWI will not start any operation as long as the TWINT bit in TWCR is set.

Immediately after the application has cleared TWINT, the TWI will initiate transmission

of the STOP condition. Note that TWINT is NOT set after a STOP condition has been

sent.

Even though this example is simple, it shows the principles involved in all TWI transmissions.

These can be summarized as follows:

• When the TWI has finished an operation and expects application response, the TWINT Flag

is set. The SCL line is pulled low until TWINT is cleared.

AT90SCR100 데이터시트(PDF) 306 Page - ATMEL Corporation

AT90SCR100 데이터시트(HTML) 306 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

데이터시트 다운로드

링크 URL