Philips Semiconductors

Product specification

PTN3501

Maintenance and control device

2001 Jan 17

8

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.

Byte Write (see Figure 14)

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

slave address and the R/W bit set to 0. The PTN3501 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 PTN3501 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 15)

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

PTN3501 considers subsequent words as data. After each data

word the PTN3501 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.

P

SW00651

SDA

SLAVE

ADDRESS

(MEMORY)

WORD

ADDRESS

DATA

S

1 A5 A4 A3 A2 A1 A0

A

A

R/W

START CONDITION

STOP

CONDITION

0A

ACKNOWLEDGE

FROM SLAVE

ACKNOWLEDGE

FROM SLAVE

ACKNOWLEDGE

FROM SLAVE

Figure 14. Byte write

S

P

SDA

SW00652

SLAVE ADDRESS

(MEMORY)

WORD ADDRESS

DATA TO MEMORY

1 A5A4 A3 A2A1 A0

AA

0

START

CONDITION

R/W

ACKNOWLEDGE

FROM SLAVE

ACKNOWLEDGE

FROM SLAVE

DATA n

A

ACKNOWLEDGE

FROM SLAVE

DATA +3n

DATA TO MEMORY

STOP

CONDITION

A

Figure 15. Page Write