ATmega32HVB datasheet(169/273 Pages) ATMEL

169 / 273 page

169

8042A–AVR–07/09

ATmega16HVB/32HVB

Figure 27-11. 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 Table 27-2). In order to enter MT mode,

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 acknowledgment 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 Table 27-2.

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:

This scheme is repeated until the last byte has been sent and the transfer is ended by generat-

ing a STOP condition or a repeated START condition. A STOP condition is generated by writing

the following value to TWCR:

TWCR

TWINT

TWEA

TWSTA

TWSTO

TWWC

TWEN

–

TWIE

Value

TWCR

TWINT

TWEA

TWSTA

TWSTO

TWWC

TWEN

–

TWIE

Value

TWCR

TWINT

TWEA

TWSTA

TWSTO

TWWC

TWEN

–

TWIE

Value

TWCR

TWINT

TWEA

TWSTA

TWSTO

TWWC

TWEN

–

TWIE

Value

Device 1

MASTER

TRANSMITTER

Device 2

SLAVE

RECEIVER

Device 3

Device n

SDA

SCL

........

BUS

ATmega32HVB датащи(PDF) 169 Page - ATMEL Corporation

ATmega32HVB датащи(HTML) 169 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

датащи скачать

ссылки URL