13

Table 9. Control Functions: Low Speed Signals Timing Characteristics

The following characteristics are defined over the Recommended Operating Conditions unless otherwise noted.

Parameter

Symbol

Minimum

Maximum

Unit

Notes

TX_DISABLE Assert Time

t_off

10

µs

Note 1 , Fig. 6

TX_DISABLE Negate Time

t_on

2

ms

Note 2 , Fig. 6

Time to initialize, including reset of TX_FAULT t_init

300

ms

Note 3 , Fig. 6

TX_FAULT Assert Time

t_fault

1

ms

Note 4 , Fig. 6

TX_DISABLE to Reset

t_reset

10

µs

Note 5 , Fig. 6

RX_LOS Assert Time

t_los_on

100

µs

Note 6 , Fig. 6

RX_LOS Deassert Time

t_los_off

100

µs

Note 7 , Fig. 6

Notes:

1. Time from rising edge of TX_DISABLE to when the optical output falls below 10% of nominal. A 10 ms interval between assertions of TX_

DISABLE is required.

2. Time from falling edge of TX_DISABLE to when the modulated optical output rises above 90% of nominal.

3. Time from power on or falling edge of TX_DISABLE to when the modulated optical output rises above 90% of nominal and the Two-Wire

interface is available.

4. From power on or negation of TX_FAULT using TX_DISABLE.

5. Time TX_DISABLE must be held high to reset the laser fault shutdown circuitry.

6. Time from loss of optical signal to Rx_LOS Assertion.

7. Time from valid optical signal to Rx_LOS De-Assertion.

Table 10. Control Functions: Two-Wire Interface Timing Characteristics

The following characteristics are defined over the Recommended Operating Conditions unless otherwise noted.

Parameter

Symbol

Minimum

Maximum

Unit

Notes

TX_DISABLE Assert Time

t_off_twi

100

ms

Note 1

TX_DISABLE Negate Time

t_on_twi

100

ms

Note 2

TX_FAULT Assert Time

t_fault_twi

100

ms

Note 3

Rx_LOS Assert Time

t_loss_on_twi

100

ms

Note 4

Rx_LOS Deassert Time

t_loss_off_twi

100

ms

Note 5

Analog parameter data ready

t_data

1000

ms

Note 6

Two-Wire Interface Ready

t_serial

300

ms

Note 7

Write Cycle Time Parameter

t_write

80

ms

Note 8

Two-Wire Interface Clock Rate

f_serial_clock

400

kHz

Note 9

Time bus free before new

transmission can start

t_BUF

20

ms

Note 10

Notes:

1. Time from two-wire interface assertion of TX_DISABLE (A2h, byte 110, bit 6) to when the optical output falls below 10% of nominal. Measured

from falling clock edge after stop bit of write transaction.

2. Time from two-wire interface de-assertion of TX_DISABLE (A2h, byte 110, bit 6) to when the modulated optical output rises above 90% of

nominal.

3. Time from fault to two-wire interface TX_FAULT (A2h, byte 110, bit 2) asserted.

4. Time for two-wire interface assertion of Rx_LOS (A2h, byte 110, bit 1) from loss of optical signal.

5. Time for two-wire interface de-assertion of Rx_LOS (A2h, byte 110, bit 1) from presence of valid optical signal.

6. From power on to data ready bit asserted (A2h, byte 110, bit 0). Data ready indicates analog monitoring circuitry is functional.

7. Time from power on until module is ready for data transmission over the two-wire interface (reads or writes over A0h and A2h).

8. Time from stop bit to completion of a 1-8 byte write command. For a one to four byte write the maximum cycle time is 40ms and for a five to

eight byte write the maximum cycle time is 80ms.

9. Module may clock stretch for f_serial_clock greater than 100 kHz.

10. Between STOP and START. See SFF 8431 Section 4.3