15

4872A–CORD–08/05

U4091BM-R

10.1

Power-on Reset

To avoid undefined states of the system when it is powered on, an internal reset clears the inter-

nal registers.

The system (U4091BM-R + microcontroller) is woken up by any of the following conditions:

• VMP > 2.75V and VB > 2.95V

• and line voltage (VL)

• or ringer (VRING)

• or external supply (ES)

The power-down of the circuit is caused by a shut-down sent by the serial bus (SD = 1), low-volt-

age reset, or by the watchdog function (see Figure 12-2 on page 17, Figure 12-3 on page 17 and

Figure 12-4 on page 17).

11. Watchdog Function

To avoid the system operating the microcontroller in a fault state, the circuit provides a watchdog

function. The watchdog has to be retriggered every second by triggering the serial bus (sending

information to the IC or other remote components at the serial bus). If there has been no bus

transmission for more than one second, the watchdog initiates a reset.

The watchdog provides a reset for the external microcontroller, but does not change the

U4091BM-R’s registers.

R14

TM

CLOR

R14B0

TME2

Test mode enable (high active)

0

R14B1

TME3

Test mode enable (low active)

0

R14B2

Reserved

-

0

R14B3

CLOR0

Adjustment for calculated receive log amp LSB

0

R14B4

CLOR1

Adjustment for calculated receive log amp

0

R14B5

CLOR2

Adjustment for calculated receive log amp

0

R14B6

CLOR3

Adjustment for calculated receive log amp

0

R14B7

CLOR4

Adjustment for calculated receive log amp MSB

0

R15

CLOT

R15B0

Reserved

-

0

R15B1

Reserved

-

0

R15B2

Reserved

-

0

R15B3

CLOT0

Adjustment for calculated transmit log amp LSB

0

R15B4

CLOT1

Adjustment for calculated transmit log amp

0

R15B5

CLOT2

Adjustment for calculated transmit log amp

0

R15B6

CLOT3

Adjustment for calculated transmit log amp

0

R15B7

CLOT4

Adjustment for calculated transmit log amp MSB

0

Table 10-6.

Names and Functions of the Serial Registers (Continued)

Register

Group

No.

Name

Description

Status