DP7409

© NIDEC COPAL ELECTRONICS CORP.

7

Doc. No. MD-2010 Rev. K

Characteristics subject to change without notice

WRITE OPERATIONS

In the

Write mode, the Master device sends the

START condition and the slave address information to

the Slave device. After the Slave generates an

acknowledge, the Master sends the instruction byte

that defines the requested operation of DP7409. The

instruction byte consist of a four-bit opcode followed

by two register selection bits and two pot selection

bits. After receiving another acknowledge from the

Slave, the Master device transmits the data to be

written into the selected register. The DP7409

acknowledges once more and the Master generates

the STOP condition, at which time if a non-volatile

data register is being selected, the device begins an

internal programming cycle to non-volatile memory.

While this internal cycle is in progress, the device will

not respond to any request from the Master device.

Acknowledge Polling

The disabling of the inputs can be used to take

advantage of the typical write cycle time. Once the

stop condition is issued to indicate the end of the

host's write operation, the DP7409 initiates the

internal write cycle. ACK polling can be initiated

immediately. This involves issuing the start condition

followed by the slave address. If the DP7409 is still

busy with the write operation, no ACK will be returned.

If the DP7409 has completed the write operation, an

ACK will be returned and the host can then proceed

with the next instruction operation.

WRITE PROTECTION

The Write Protection feature allows the user to protect

against inadvertent programming of the non-volatile

data registers. If the WP

¯¯¯ pin is tied to LOW, the data

registers are protected and become read only.

Similarly, the WP

¯¯¯ pin going low after start but after

start will interrupt non-volatile write to data registers,

while the WP

¯¯¯ pin going low after internal write cycle

has started, will have no effect on any write operation.

The DP7409 will accept both slave addresses and

instructions, but the data registers are protected from

programming by the device’s failure to send an

acknowledge after data is received.

Figure 5. Slave Address Bits

DP7409

0

1

0

1

A3

A2

A1

A0

*

A0, A1, A2 and A3 correspond to pin A0, A1, A2 and A3 of the device.

**

A0, A1, A2 and A3 must compare to its corresponding hard wired input pins.

Figure 6. Write Timing

S

A

C

K

A

C

K

DR1 WCRDATA

S

T

O

P

P

BUS ACTIVITY:

MASTER

SDA LINE

S

T

A

R

T

A

C

K

SLAVE/DP

ADDRESS

INSTRUCTION

BYTE

Fixed

Variable

op code

Register

Address

Pot/WCR

Address