X9525 Datasheet, PDF (6/26 Pages) Intersil Corporation – Fiber Channel/Gigabit Etherner Laser Diode Control for Fiber Optic Modules

X9525
Vcc
Vcc (Max.)
V_TRIP
t_trans
t_pu
t
0
Maximum Wiper Recall time
Figure 7. DCP Power-up
Hot Pluggability
Figure 7 shows a typical waveform that the X9525 might
experience in a Hot Pluggable situation. On power-up,
Vcc applied to the X9525 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 sys-
tem 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
X9525 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 1010A₀11. 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) performed.
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 and NVM. Therefore, the new “wiper position” set-
ting is recalled into the WCR after Vcc of the X9525 has
been powered down then powered back up
If WT is “0” then a DCP Volatile Write is performed. This
operation changes the DCP “wiper position” by writing
new data to the associated WCR only. The contents of
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FN8210.0
March 10, 2005