X9525 Datasheet, PDF (8/26 Pages) Intersil Corporation – Fiber Channel/Gigabit Etherner Laser Diode Control for Fiber Optic Modules

X9525
Signals from
the Master
SDA Bus
Signals from
the Slave
WRITE Operation
READ Operation
S
S
t
a
r
Slave
Address
Instruction
Byte
t
a
r
Slave
Address
S
t
Data Byte o
t
t
p
10
1
0
A
0
1
1
0
W
T
00000
P
1
P
0
1
0
1
0
A
0
1
1
1
A
A
A
C
C
C
K
K
K
“Dummy” write
Figure 10. DCP Read Sequence
DCPx
-
x=1
MSB
LSB
“-” = DON’T CARE
x=2
It should be noted that all writes to any DCP of the X9525
are random in nature. Therefore, the Data Byte of con-
secutive write operations to any DCP can differ by an
arbitrary number of bits. Also, setting the bits (P1 = 0,
P0 = 0) or (P1 = 1, P0 = 1) are reserved sequences, and
will result in no ACKNOWLEDGE after sending an
Instruction Byte on SDA.
The factory default setting of all “wiper position” settings
is with 00h stored in the NVM of the DCPs. This corre-
sponds to having the “wiper teminal” R_WX (x = 1,2) at the
“lowest” tap position, therefore, the resistance between
R_WX and R_LX is a minimum (essentially only the Wiper
Resistance, R_W).
DCP Read Operation
A read of DCPx (x = 1,2) can be performed using the
three byte random read command sequence shown in
Figure 10.
The master issues the START condition and the Slave
Address Byte 1010A₀110 which specifies that a
“dummy” write” is to be conducted. This “dummy” write
operation sets which DCP is to be read (in the preceding
Read operation). An ACKNOWLEDGE is returned by the
X9525 after the Slave Address if received correctly. Next,
an Instruction Byte is issued on SDA. Bits P1 - P0 of the
Instruction Byte determine which DCP “wiper position” is
to be read. In this case, the state of the WT bit is “don’t
care”. If the Instruction Byte format is valid, then another
ACKNOWLEDGE is returned by the X9525.
Following this ACKNOWLEDGE, the master immediately
issues another START condition and a valid Slave
address byte with the R/W bit set to 1. Then the X9525
issues an ACKNOWLEDGE followed by Data Byte, and
finally, the master issues a STOP condition. The Data
Byte read in this operation, corresponds to the “wiper
position” (value of the WCR) of the DCP pointed to by
bits P1 and P0.
Signals from
the Master
S
t
WRITE Operation
a
r
Slave
Address
t _Address
Byte
S
t
Data
o
Byte
p
SDA Bus
1
0
1
0
A
0
0
0
0
Signals from
the Slave
A
A
A
Internal _C
C
C
Device
Address
K
K
K
Figure 11. EEPROM Byte Write Sequence
8
FN8210.0
March 10, 2005