DS1876 datasheet(45/69 Pages) MAXIM

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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 I2C 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 I2C 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 I2C 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

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)

TINDEX6

TINDEX5

TINDEX4

TINDEX3

TINDEX2

TINDEX1

TINDEX0

Table 06h (APC)

TINDEX6

TINDEX5

TINDEX4

TINDEX3

TINDEX2

TINDEX1

TINDEX0

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

TEMP (NC)

< -8

-8 to +8

+8 to +24

+24 to +40

+40 to +56

+56 to +72

+72 to +88

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