X9523 Datasheet, PDF (6/30 Pages) Intersil Corporation – Laser Diode Control for Fiber Optic Modules

X9523
final STOP condition), the X9523 initiates an internal high
voltage write cycle. This cycle typically requires 5 ms.
During this time, no further Read or Write commands can
be issued to the device. Write Acknowledge Polling is
used to determine when this high voltage write cycle has
been completed.
To perform acknowledge polling, the master issues a
START condition followed by a Slave Address Byte. The
Slave Address issued must contain a valid Internal
Device Address. The LSB of the Slave Address (R/W)
can be set to either 1 or 0 in this case. If the device is still
busy with the high voltage cycle then no
ACKNOWLEDGE will be returned. If the device has
completed the write operation, an ACKNOWLEDGE will
be returned and the host can then proceed with a read or
write operation. (Refer to Figure 5.).
Byte load completed
by issuing STOP.
Enter ACK Polling
N
R_Hx
WIPER
COUNTER
REGISTER
(WCR)
NON
VOLATILE
MEMORY
(NVM)
DECODER
2
1
0
“WIPER”
FET
SWITCHES
RESISTOR
ARRAY
R_Lx
R_Wx
Figure 6. DCP Internal Structure
Issue START
Issue Slave Address
Byte (Read or Write)
Issue STOP
ACK
returned?
YES
High Voltage Cycle
complete. Continue
command sequence?
NO
NO
YES
Continue normal
Read or Write
command sequence
Issue STOP
PROCEED
Figure 5. Acknowledge Polling Sequence
DIGITALLY CONTROLLED POTENTIOMETERS
DCP Functionality
The X9523 includes two independent resistor arrays.
These arrays respectively contain 99 and 255 discrete
resistive segments that are connected in series. The
physical ends of each array are equivalent to the fixed
terminals of a mechanical potentiometer (R_Hx and R_Lx
inputs - where x = 1,2).
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 X9523, wiper position data is auto-
matically 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
R₁ / 100 TAP
R₂ / 256 TAP
Initial Values Before Recall
V_L / TAP = 0
V_H / TAP = 255
6
FN8209.0
March 10, 2005