ATmega32A datasheet(203/352 Pages) ATMEL

203 / 352 page

203

8155B–AVR–07/09

ATmega32A

• Bit 2 – TWEN: TWI Enable Bit

The TWEN bit enables TWI operation and activates the TWI interface. When TWEN is written to

one, the TWI takes control over the I/O pins connected to the SCL and SDA pins, enabling the

slew-rate limiters and spike filters. If this bit is written to zero, the TWI is switched off and all TWI

transmissions are terminated, regardless of any ongoing operation.

• Bit 1 – Res: Reserved Bit

This bit is a reserved bit and will always read as zero.

• Bit 0 – TWIE: TWI Interrupt Enable

When this bit is written to one, and the I-bit in SREG is set, the TWI interrupt request will be acti-

vated for as long as the TWINT Flag is high.

20.9.3

TWSR – TWI Status Register

• Bits 7:3 – TWS: TWI Status

These five bits reflect the status of the TWI logic and the Two-wire Serial Bus. The different sta-

tus codes are described later in this section. Note that the value read from TWSR contains both

the 5-bit status value and the 2-bit prescaler value. The application designer should mask the

prescaler bits to zero when checking the Status bits. This makes status checking independent of

prescaler setting. This approach is used in this datasheet, unless otherwise noted.

• Bit 2 – Res: Reserved Bit

This bit is reserved and will always read as zero.

• Bits 1:0 – TWPS: TWI Prescaler Bits

These bits can be read and written, and control the bit rate prescaler.

To calculate bit rates, see “Bit Rate Generator Unit” on page 182. The value of TWPS1:0 is used

in the equation.

20.9.4

TWDR – TWI Data Register

Bit

7654

321

TWS7

TWS6

TWS5

TWS4

TWS3

–

TWPS1

TWPS0

TWSR

Read/Write

RRRR

R/W

Initial Value

1111

100

Table 20-7.

TWI Bit Rate Prescaler

TWPS1

TWPS0

Prescaler Value

Bit

765

432

TWD7

TWD6

TWD5

TWD4

TWD3

TWD2

TWD1

TWD0

TWDR

Read/Write

R/W

Initial Value

ATmega32A Datasheet(PDF) 203 Page - ATMEL Corporation

ATmega32A Datasheet(HTML) 203 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

Datasheet Download

Link URL