Rainbow Electronics DS1876 - Manual (Page 45)

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DS1876
SFP Controller with Dual LDD Interface
Table 02h, Register 80h: MODE (continued)
Table 02h, Register 81h: TEMPERATURE INDEX (TINDEX)
BIT 2
MOD1EN:
0 = MOD1 DAC is writable by the user and the LUT recalls are disabled. This allows the user to
interactively test their modules by writing the values for MOD1. The output is updated with the new
value at the end of the write cycle. The I
2 C STOP condition is the end of the write cycle.
1 = (default) Enables automatic control of the LUT for MOD1 DAC.
BIT 1
QT1EN:
0 = QTs (HBIAS, TXP HI, TXP LO) for transmitter 1 are writable by the user and the LUT recalls are
disabled. This allows the user to interactively test their modules by writing to the QT thresholds.
The thresholds are updated with the new values at the end of the write cycle. The I
2 C STOP
condition is the end of the write cycle.
1 = (default) Enables automatic control of the LUT QTs for transmitter 1.
BIT 0
APC1EN:
0 = APC1 DAC is writable by the user and the LUT recalls are disabled. This allows the user to
interactively test their modules by writing the values for APC1. The output is updated with the new
value at the end of the write cycle. The I
2 C STOP condition is the end of the write cycle.
1 = (default) Enables automatic control of the LUT for APC1 DAC.
FACTORY DEFAULT 00h
READ ACCESS PW2 or (PW1 and RWTBL2) or (PW1 and RTBL2)
WRITE ACCESS (PW2 and AEN = 0) or (PW1 and RWTBL2 and AEN = 0)
A2h AND B2h MEMORY Common A2h and B2h memory location
MEMORY TYPE Volatile
81h 2 7 2 6 2 5 2 4 2 3 2 2 2 1 2 0
BIT 7 BIT 0
Holds the calculated index based on the temperature measurement. This index is used for the address during lookup
of Tables 04h and 06h. Temperature measurements below -40NC or above +102NC are clamped to 80h and C7h,
respectively. The calculation of TINDEX is as follows:
Temp_Value 40 C
TINDEX 80h
2 C
+ °
= +
°
For the temperature-indexed LUTs (2NC), the index used during the lookup function for each table is as follows:
Table 04h (MOD)
1 TINDEX
6
TINDEX
5
TINDEX
4
TINDEX
3
TINDEX
2
TINDEX
1
TINDEX
0
Table 06h (APC) 1 TINDEX 6 TINDEX 5 TINDEX 4 TINDEX 3 TINDEX 2 TINDEX 1 TINDEX 0
For the 8-position LUT tables, the following table shows the lookup function:
TINDEX
1000_0xxx 1001_0xxx 1001_1xxx 1010_0xxx 1010_1xxx 1011_0xxx 1011_1xxx 11xx_xxxx
BYTE F8 F9 FA FB FC FD FE FF
TEMP (NC) < -8 -8 to +8 +8 to +24 +24 to +40 +40 to +56 +56 to +72 +72 to +88 R 88