X9409 datasheet(4/21 Pages) XICOR

4 / 21 page

X9409 – Preliminary Information

Characteristics subject to change without notice.

4 of 21

REV 1.6 1/30/03

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Acknowledge Polling

The disabling of the inputs, during the internal

nonvolatile write operation, can be used to take

advantage of the typical nonvolatile write cycle time.

Once the stop condition is issued to indicate the end of

the nonvolatile write command the X9409 initiates the

internal write cycle. ACK polling can be initiated

immediately. This involves issuing the start condition

followed by the device slave address. If the X9409 is

still busy with the write operation no ACK will be

returned. If the X9409 has completed the write

operation an ACK will be returned and the master can

then proceed with the next operation.

Flow 1. ACK Polling Sequence

Instruction Structure

The next byte sent to the X9409 contains the

instruction and register pointer information. The format

is shown in Figure 2.

Figure 2. Instruction Byte Format

The four high order bits deﬁne the instruction. The next

two bits (R1 and R0) select one of the four registers

that is to be acted upon when a register oriented

instruction is issued. The last bits (P1, P0) select

which one of the four potentiometers is to be affected

by the instruction.

Four of the nine instructions end with the transmission

of the instruction byte. The basic sequence is

illustrated in Figure 3. These two-byte instructions

exchange data between the Wiper Counter Register

and one of the data registers. A transfer from a Data

write to a static RAM. The response of the wiper to this

action will be delayed tWRL. A transfer from the Wiper

Counter Register (current wiper position), to a Data

minimum of tWR to complete. The transfer can occur

between one of the four potentiometers and one of its

associated registers; or it may occur globally, wherein

the transfer occurs between all of the potentiometers

and one of their associated registers.

Four instructions require a three-byte sequence to

complete. These instructions transfer data between

the host and the X9409; either between the host and

one of the data registers or directly between the host

and the Wiper Counter Register. These instructions

are: Read Wiper Counter Register (read the current

wiper position of the selected pot), Write Wiper

Counter Register (change current wiper position of the

selected pot), Read Data Register (read the contents

of the selected nonvolatile register) and Write Data

Figure 4.

Nonvolatile Write

Command Completed

Enter ACK Polling

Issue

START

Issue Slave

Address

ACK

Returned?

Further

Operation?

Issue

Instruction

Issue STOP

YES

Proceed

Issue STOP

Proceed

Pot Select

Select

Instructions

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