CPU Supervisor with Nonvolatile Memory and

Programmable I/O

10

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address pin allows for the DS4510 to respond to one of

two slave addresses (1010000X, or 1010001X). If the

R/

W bit is zero, the master writes data to the slave. If

the R/

W is one, the master reads data from the slave.

master must transmit a memory address to identify the

memory location where the slave is to store the data.

The memory address is always the second byte trans-

mitted during a write operation following the slave

address byte (R/

W = 0).

Writing a Single Byte to a Slave: The master must

generate a start condition, write the slave address

(R/

W= 0), write the memory address, write the byte of

data and generate a stop condition. Remember the

master must read the slave’s acknowledgement during

all byte write operations.

Writing a Multiple Bytes to a Slave: To write multiple

bytes to a slave the master generates a start condition,

writes the slave address (R/

W = 0), writes the memory

address, writes up to 8 data bytes, and generates a

stop condition.

The DS4510 can write 1 to 8 bytes (one page or row)

with a single write transaction. This is internally con-

trolled by an address counter that allows data to be

written to consecutive addresses without transmitting a

memory address before each data byte is sent. The

address counter limits the write to one 8-byte page

to write to additional pages of memory without sending

a stop condition between pages results in the address

counter wrapping around to the beginning of the pre-

sent row.

Example: A 3-byte write starts at address 06h and

writes three data bytes (11h, 22h, and 33h) to three

“consecutive” addresses. The result would be address-

es 06h and 07h would contain 11h and 22h, respective-

ly, and the third data byte, 33h, would be written to

address 00h.

To prevent address wrapping from occurring, the mas-

ter must send a stop condition at the end of the page,

then wait for the bus-free or EEPROM-write time to

elapse. The master may then generate a new start con-

START

STOP

SDA

SCL

REPEATED

START

7-BIT SLAVE ADDRESS

MOST

SIGNIFICANT BIT

10

1

000

A0 PIN

VALUE

DETERMINES

READ OR WRITE

Figure 6. DS4510’s Slave Address and the R/

W Bit