AS-Interface Slave IC

AS2701A (ISA3+)

Rev. C, October 2000

Page 12 of 16

Reset Behaviour

The AS-Interface Slave IC can be in reset condition or reset by the following events:

• at power-up of VLTGP: as long as VUOUT has not yet reached the treshold voltage

9 V

• at power-down of VLTGP: as soon as U5R drops below the treshold voltage

3.5 V

• by a 'L' input level to DSTBn for more than 44 µs;

• resulting from a “Reset AS-Interface Slave“- command by the AS-Interface Master

over the AS-Interface BUS.

The different levels of VCOMOFF and VPOR as per a) and b) and the fact that the U5R supply

voltage results from a down-regulation of the VUOUT supply assure a desirable hysteresis in

the order of several volts between the VUOUT power-on-reset and power-down-reset

threshold. Whereas at power-up the AS-Interface Slave IC is released from reset by VUOUT

reaching a level of between 9 V and 11 V, at power-down VUOUT has to come down to a level

in the order of 5 V for U5R to drop into the reset-triggering window between 3.5 V and 4 V.

Some different power-down events are illustrated below:

t

Loff

1

VLTGP

18 V

0 V

POR

(internal signal)

neither receive

nor transmit

2

(no reset)

VUOUT

VCOMOFF

VUOUT

VCOMOFF

VU5R

VPOR

(reset)

3

Notes:

as to (1):

No reset will be triggered, if VLTGP is lower than 18 V for less than 1 ms

as to (2):

If VUOUT < VCOMOFF but still U5R > VPOR, communication over the Data

Port is inhibited, but no reset triggered

as to (3):

If U5R < VPOR (resulting from VUOUT << VCOMOFF), a reset is triggered.

Reset is overcome as soon as VUOUT > VCOMOFF (implying U5R > VPOR)

In reset condition internal registers are cleared and data port D0...D3 is switched into high-

impedant condition. After release from reset the AS-Interface Slave automatically performs a

first read cycle to clear the E

a second one to load the AS-Interface address, IO Configuration and ID Code into its internal

registers.

Symbol

Parameter

min

max

Unit

Note

t reset

Reset Time after the Master

Command “Reset AS-Interface Slave”

or DSTBn = ext. L/H-Edge

2

ms

t reset2

Reset Time after Power On

30

ms

t reset3

Reset Time after Power On with great

Load Capacity

1000

ms

CUOUT = 470 µF

t Loff

Voltage Breakdown Time

1

ms

CUOUT > 10 µF

VCOMMoff

Voltage for “Communication OFF”

9

11

V

VPOR

Voltage for Internal Reset

3.5

4

V