PIC12CE519T-04 查看數據表（PDF） - Microchip Technology

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PIC12CE519T-04

8-Pin, 8-Bit CMOS Microcontrollers

Microchip Technology 

PIC12C5XX

FIGURE 7-3: DATA TRANSFER SEQUENCE ON THE SERIAL BUS

SCL (A)

(B)

(C)

(D)

SDA

START

CONDITION

ADDRESS OR

ACKNOWLEDGE

VALID

DATA

ALLOWED

TO CHANGE

(C) (A)

STOP

CONDITION

FIGURE 7-4: ACKNOWLEDGE TIMING

Acknowledge

Bit

SCL

12 345678 9 123

SDA

Data from transmitter

Transmitter must release the SDA line at this point

allowing the Receiver to pull the SDA line low to

acknowledge the previous eight bits of data.

Data from transmitter

Receiver must release the SDA line at this point

so the Transmitter can continue sending data.

7.2 Device Addressing

After generating a START condition, the bus master

transmits a control byte consisting of a slave address

and a Read/Write bit that indicates what type of opera-

tion is to be performed. The slave address consists of

a 4-bit device code (1010) followed by three don’t care

bits.

The last bit of the control byte determines the operation

to be performed. When set to a one a read operation is

selected, and when set to a zero a write operation is

selected. (Figure 7-5). The bus is monitored for its cor-

responding slave address all the time. It generates an

acknowledge bit if the slave address was true and it is

not in a programming mode.

FIGURE 7-5: CONTROL BYTE FORMAT

Read/Write Bit

Device Select

Bits

Don’t Care

Bits

S 1 0 1 0 X X X R/W ACK

Start Bit

Slave Address

Acknowledge Bit

DS40139E-page 32

© 1999 Microchip Technology Inc.

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