DS1864 datasheet(21/72 Pages) DALLAS

21 / 72 page

SFP Laser Controller and

Diagnostic IC

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shutdown signals. Alarm and warning thresholds keep

the system functioning within user-programmed para-

meters. All alarm and warning flags are active high.

Fast-trip alarms and warnings can be configured to

overwrite the diagnostic flags for the same function.

Laser safety features are also implemented to accept

and send alarm signals to control laser activity.

Fast-Trips

The three monitor channels (MON1, MON2, and MON3)

have associated fast channels. A sequencer with fast-trip

comparators monitors the three voltage channels: MON1

(Bias Current (IBI)), MON2 (Transmitted Power (TXP)),

and MON3 (Received Power (RIN)). These signals are the

same raw (uncalibrated) signals used for the diagnostic

circuits. Five fast-trip flags (alarms and warnings) are

generated: high-bias alarm (HBAL), high-bias warning

(HBWA), high transmitted power (HTXP), low transmitted

power (LTXP), and loss of received signal (LOS), see

Figure 12. These flags are located in Lower Memory, byte

73h. These flags are latched temporarily by design as

required by the sequencer. In order to disable a com-

parator, set its threshold to 00h for low flags and FFh for

high flags. The FT_enable bit (bit 3, byte 80h, Table 04h

(Table 01h in DS1859 configuration)) determines if fast-

trip alarms are enabled or disabled.

The thresholds for HBAL and HBWA can be pro-

grammed to be temperature compensated. Registers

B0h to B7h for HBAL and B8h to BFh for HBWA of

Table 04h (Table 01h in DS1859 configuration) are

where the temperature-compensated alarm and warn-

ing thresholds are stored. Register DBh of Table 04h

(Table 01h in DS1859 configuration) is the location of

the HTXP programmable threshold. Register DCh of

Table 7. MON3 Configuration Registers

FINE MODE

COURSE

GAIN REGISTER

98 to 99h,

Table 04h*

9A to 9Bh,

Table 04h*

OFFSET REGISTER

A8 to A9h,

Table 04h*

AA to ABh,

Table 04h*

RIGHT SHIFT REGISTER

8Fh,

Table 04h*

N/A

RSSIC AND RSSIF BITS

8Ah, Table 04h*

RSSIS BIT

77h, Lower Memory

MON3 MEASUREMENT

68 to 69h, Lower Memory

*Table 04h in DS1852 configuration or Table 01h in DS1859

configuration.

Table 6. MON3 Hysteresis Threshold

Values

# OF RIGHT

SHIFTS

FINE MODE MAX

(HEX)

COURSE MODE

MIN* (HEX)

FFF8

F000

7FFC

7800

3FFE

3C00

1FFF

1E00

0FFF

0F00

07FF

0780

03FF

03C0

01FF

01E0

*This is the minimum reported course mode conversion.

MON3

TIMESLICE

END OF MON3

TIMESLICE

PERFORM FINE

MODE CONVERSION

REPORT FINE

CONVERSION RESULT

REPORT COURSE

CONVERSION RESULT

DID PRIOR MON3

TIMESLICE RESULT IN A

COURSE CONV.?

(RSSIS = 1?)

RSSIS BIT = 0

RSSIS BIT = 1

WAS CURRENT FINE

MODE CONV. <

COURSE MIN?

PERFORM COURSE

MODE CONVERSION

DID CURRENT FINE

MODE CONV.

REACH MAX?

Figure 15. Dual-Range Functionality Flowchart

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