
AS2702 – AS-Interface Slave IC
Revision 1.3, 21-Aug-08
Page 10 of 13
Operation Status Pins LED1 and LED2
Pins LED1 and LED2 are both equipped with a low-side open-drain output switch plus a passive high-side current source with a
nom. 10μA pull-up current capability. They will each have an LED load connected to UOUT, which will flag the operation status of
the slave device, according to the following table:
Output LED1
Output LED2
Flagging Priority
(green LED
connected)
connected)
4 = lowest)
off
off
on
off
off
of
4
Slave Device
Operation Status
Reason
(red LED
(1 = highest, …,
Supply voltage off
Regular operation
No data communication
No supply voltage
Regular, non-zero slave address
coded; data comm. watchdog
triggered
Slave address = default zero
blinks
on
3
No regular slave address
coded
Hardware failure in
sensor/actuator circuitry
External RESET or
overload at UOUT pin
blinks
blinks (alternating
with LED1)
blinks
2
Input PFAULT = L
off
1
DSTBn = L to RESET, or UOUT
switched-off due to overload
(LED1 and LED2 both also feature an input stage, to simplify component test and shorten test time of the slave device.)
The dc- and timing parameters of pins LED1 and LED2 are specified as follows:
Symbol
Parameter
ILED
Sink current @ output L
IOUTHI
Leakage current @ output off
VIN
Acceptable input voltage @ output off
fBLINK
Blinking frequency
Min
10
-10
-0.3
2
Max
10
40
3
Unit Note
mA VOUT = 1V
μA VOUT = 5V
V
Hz
Data Communication Watchdog
AS2702 is equipped with a watchdog timer to supervise data communication by monitoring the strobe signals at pins DSTBn and
PSTBn.
If a parameter or data strobe is not followed by a consecutive strobe within a time period of 50 … 100ms, the watchdog is triggered
and initiates a ‘soft’ reset, see section Reset.
Reset
There are 2 categories of reset-events, leading to 2 slightly different reset-conditions of the slave device:
1
A ‘hard’ reset taking place at power-up and power-down of supply-voltages U5R and UOUT.
At power-up the slave device leaves reset-condition as soon as U5R has passed 3.75V and UOUT has passed VCOMOFF =
nom. 10V.
At power-down the slave device is forced into reset-condition as soon as U5R drops below 3.75V.
(Tolerance of the threshold voltages referred to is
±
5 %)
2
A ‘soft’ reset, resulting from one of the following events:
2.1
Data strobe pin DSTBn is kept L for more than 100ms;
2.2
Master command ‘RESET SLAVE’ is received;
2.3
Master command ‘RESET BROADCAST’ is received;
2.4
The communication watchdog is triggered.