X9521 Datasheet, PDF (6/26 Pages) Xicor Inc. – Dual DCP, EEPROM Memory

X9521 – Preliminary Information
Vcc
Vcc (Max.)
V_TRIP
t_trans
t_pu
t
0
Maximum Wiper Recall time
Figure 7. DCP Power up
before break” sequence is used internally for the FET
switches when the wiper is moved from one tap position
to another.
Hot Pluggability
Figure 7 shows a typical waveform that the X9521 might
experience in a Hot Pluggable situation. On power up,
Vcc applied to the X9521 may exhibit some amount of
ringing, before it settles to the required value.
The device is designed such that the wiper terminal (R_Wx)
is recalled to the correct position (as per the last stored in
the DCP NVM), when the voltage applied to Vcc exceeds
V_TRIP for a time exceeding t_pu.
Therefore, if t_trans is defined as the time taken for Vcc to
settle above V_TRIP (Figure 7): then the desired wiper ter-
minal position is recalled by (a maximum) time: t_trans +
t_pu. It should be noted that t_trans is determined by system
hot plug conditions.
DCP Operations
In total there are three operations that can be performed
on any internal DCP structure:
—DCP Nonvolatile Write
—DCP Volatile Write
—DCP Read
A nonvolatile write to a DCP will change the “wiper
position” by simultaneously writing new data to the
associated WCR and NVM. Therefore, the new “wiper
position” setting is recalled into the WCR after Vcc of the
X9521 is powered down and then powered back up.
A volatile write operation to a DCP however, changes the
“wiper position” by writing new data to the associated
WCR only. The contents of the associated NVM register
remains unchanged. Therefore, when Vcc to the device is
powered down then back up, the “wiper position” reverts
to that last position written to the DCP using a nonvolatile
write operation.
Both volatile and nonvolatile write operations are
executed using a three byte command sequence: (DCP)
Slave Address Byte, Instruction Byte, followed by a Data
Byte (See Figure 9)
A DCP Read operation allows the user to “read out” the
current “wiper position” of the DCP, as stored in the
associated WCR. This operation is executed using the
Random Address Read command sequence, consisting
of the (DCP) Slave Address Byte followed by an
Instruction Byte and the Slave Address Byte again (Refer
to Figure 10.).
Instruction Byte
While the Slave Address Byte is used to select the DCP
devices, an Instruction Byte is used to determine which
DCP is being addressed.
The Instruction Byte (Figure 8) is valid only when the
Device Type Identifier and the Internal Device Address
bits of the Slave Address are set to 1010111. In this
case, the two Least Significant Bit’s (I1 - I0) of the
Instruction Byte are used to select the particular DCP (0
- 2). In the case of a Write to any of the DCPs (i.e. the LSB
of the Slave Address is 0), the Most Significant Bit of the
Instruction Byte (I7), determines the Write Type (WT) per-
formed.
If WT is “1”, then a Nonvolatile Write to the DCP occurs. In
this case, the “wiper position” of the DCP is changed by
simultaneously writing new data to the associated WCR
REV 1.1.9 1/30/03
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Characteristics subject to change without notice. 6 of 26