PIC14000 datasheet(46/153 Pages) MICROCHIP

46 / 153 page

PIC14000

DS40122B-page 46

Preliminary

When a master does not wish to relinquish the bus (by

generating a STOP condition), a repeated START (Sr)

must be generated. This condition is identical to the

START (SDA goes high-to-low while SCL is high), but

occurs after a data transfer acknowledge pulse (not the

bus-free state). This allows a master to send

“commands” to the slave and then receive the

requested information or to address a different slave

device. This sequence is shown in Figure 7-10.

FIGURE 7-8:

MASTER - TRANSMITTER SEQUENCE

FIGURE 7-9:

MASTER - RECEIVER SEQUENCE

FIGURE 7-10: COMBINED FORMAT

For 7-bit address:

S Slave Address R/W A DATA A DATA A/A

"0" (write)

data transferred

(n bytes - acknowledge)

A master transmitter addresses a slave receiver with a

7-bit address. The transfer direction is not changed.

For 10-bit address:

S Slave Address

first 7 bits

R/W A1 Slave Address

second byte

(write)

A master transmitter addresses a slave receiver with a

10-bit address.

From master to slave

From slave to master

A = acknowledge (SDA low)

A = not acknowledge (SDA high)

S = START condition

P = STOP condition

Data A

Data

A/A

For 7-bit address:

S Slave Address R/W A DATA A DATA

(read)

data transferred

(n bytes - acknowledge)

A master reads a slave immediately after the first byte.

For 10-bit address:

S Slave Address

first 7 bits

R/W A1 Slave Address

second byte

(write)

A master transmitter addresses a slave receiver with a

10-bit address.

From master to slave

From slave to master

A = acknowledge (SDA low)

A = not acknowledge (SDA high)

S = START condition

P = STOP condition

Sr Slave Address

first 7 bits

R/W A3 Data A

Data

(read)

S Slave Address R/W A DATA A/A

(read or write)

(n bytes + acknowledge)

Transfer direction of data and acknowledgement bits depends on R/W bits.

Combined Format:

S Slave Address

first 7 bits

R/W A Slave Address

second byte

(write)

Combined format -

From master to slave

From slave to master

A = acknowledge (SDA low)

A = not acknowledge (SDA high)

S = START condition

P = STOP condition

Sr Slave Address

first 7 bits

R/W A Data A

Data

(read)

Sr Slave Address R/W A DATA A/A P

Sr = repeated

START condition

Direction of transfer

may change at this point

Data A

Data A/A

A master addresses a slave with a 10-bit address, then transmits

data to this slave and reads data from this slave.

(read)

(write)

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