PCA9501 datasheet(9/22 Pages) PHILIPS

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Philips Semiconductors

Product data

PCA9501

8-bit I2C and SMBus I/O port with interrupt,

2-kbit EEPROM and 6 address pins

2003 Sep 12

MEMORY OPERATIONS

Write operations

Write operations require an additional address field to indicate the

memory address location to be written. The address field is eight

bits long providing access to any one of the 256 words of memory.

There are two types of write operations, byte write and page write.

Write operation is possible when WC control pin put at a low logic

level (0). When this control signal is set at 1, write operation is not

possible and data in the memory is protected.

Byte Write and Page Write explained below assume that Write

Control pin (WC) is set to 0.

Byte Write (see Figure 11)

To perform a byte write the start condition is followed by the memory

slave address and the R/W bit set to 0. The PCA9501 will respond

with an acknowledge and then consider the next eight bits sent as

the word address and the eight bits after the word address as the

data. The PCA9501 will issue an acknowledge after the receipt of

both the word address and the data. To terminate the data transfer

the master issues the stop condition, initiating the internal write cycle

to the non-volatile memory. Only write and read operations to the

quasi-bidirectional I/Os are allowed during the internal write cycle.

Page Write (see Figure 12)

A page write is initiated in the same way as the byte write, if after

sending the first word of data, the stop condition is not received the

PCA9501 considers subsequent words as data. After each data

word the PCA9501 responds with an acknowledge and the four

least significant bits of the memory address field are incremented.

Should the master not send a stop condition after 16 data words the

address counter will return to its initial value and overwrite the data

previously written. After the receipt of the stop condition the inputs

will behave as with the byte write during the internal write cycle.

SW00651

A5 A4 A3 A2 A1 A0

SDA

ACKNOWLEDGE

FROM SLAVE

R/W

START CONDITION

ACKNOWLEDGE

FROM SLAVE

SLAVE ADDRESS (MEMORY)

WORD ADDRESS

DATA

ACKNOWLEDGE

FROM SLAVE

STOP CONDITION.

WRITE TO THE

MEMORY IS

PERFORMED

Figure 11. Byte write

SW00652

ACKNOWLEDGE

FROM SLAVE

A5 A4 A3 A2 A1 A0

SDA

ACKNOWLEDGE

FROM SLAVE

R/W

START CONDITION

ACKNOWLEDGE

FROM SLAVE

SLAVE ADDRESS (MEMORY)

WORD ADDRESS

DATA TO MEMORY

DATA n

DATA n + 3

STOP CONDITION.

WRITE TO THE MEMORY

IS PERFORMED

DATA TO MEMORY

Figure 12. Page Write

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