X9258 datasheet(4/22 Pages) XICOR

4 / 22 page

X9258

Characteristics subject to change without notice.

4 of 22

REV 1.1.7 2/4/03

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Figure 1. Slave Address

The next four bits of the slave address are the device

address. The physical device address is deﬁned by the

state of the A0-A3 inputs. The X9258 compares the

serial data stream with the address input state; a

successful compare of all four address bits is required

for the X9258 to respond with an acknowledge. The

A0–A3 inputs can be actively driven by CMOS input

signals or tied to VCC or VSS.

Acknowledge Polling

The disabling of the inputs, during the internal

nonvolatile write operation, can be used to take

advantage of the typical 5ms nonvolatile write cycle

time. Once the stop condition is issued to indicate the

end of the nonvolatile write command the X9258

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

X9258 is still busy with the write operation no ACK will

be returned. If the X9258 has completed the write

operation an ACK will be returned and the master can

then proceed with the next operation.

ACK Polling Sequence

Instruction Structure

The next byte sent to the X9258 contains the

instruction and register pointer information. The four

most signiﬁcant bits are the instruction. The next four

bits point to one of the two pots and when applicable

they point to one of four associated registers. The

format is shown below in Figure 2.

Device Type

Identifier

Device Address

Nonvolatile Write

Command Completed

EnterACK Polling

Issue

START

Issue Slave

Address

ACK

Returned?

Further

Operation?

Issue

Instruction

Issue STOP

Yes

Proceed

Issue STOP

Proceed

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