X9520_07 Datasheet, PDF (7/29 Pages) Intersil Corporation – Triple DCP, POR, 2kbit EEPROM Memory, Dual Voltage Monitors

X9520
V1/VCC
V1/VCC (Max)
V_TRIP1
t_trans
t_purst
t
0
FIGURE 7. DCP POWER
MAXIMUM WIPER RECALL TIME
At both ends of each array and between each resistor
segment there is a CMOS switch connected to the wiper
(R_wx) output. Within each individual array, only one switch
may be turned on at any one time. These switches are
controlled by the Wiper Counter Register (WCR) (See Figure
6). The WCR is a volatile register.
On power-up of the X9520, wiper position data is
automatically loaded into the WCR from its associated Non
Volatile Memory (NVM) Register. The table below shows the
Initial Values of the DCP WCR’s before the contents of the
NVM is loaded into the WCR.
DCP
R_0/64 TAP
R_1/100 TAP
R_2/256 TAP
INITIAL VALUES BEFORE RECALL
V_H/TAP = 63
V_L/TAP = 0
V_H/TAP = 255
The data in the WCR is then decoded to select and enable
one of the respective FET switches. A “make 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 X9520 might
experience in a Hot Pluggable situation. On power-up,
V1/VCC applied to the X9520 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 V1/VCC exceeds
V_TRIP1 for a time exceeding t_purst (the Power-on Reset
time, set in the CONSTAT Register - See “Control and Status
Register” on page 12.).
Therefore, if t_trans is defined as the time taken for V1/VCC
to settle above V_TRIP1 (Figure 7): then the desired wiper
terminal position is recalled by (a maximum) time: t_trans +
t_purst. 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 V1/VCC of the X9520 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 V1/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.
7
FN8206.2
August 20, 2007