ASI4U datasheet(53/64 Pages) ETC2

53 / 64 page

ASI4U / ASI4U-E / ASI4U-F

Spec. 3.0 Compliant Universal AS-I IC

Data Sheet

April 2, 2012

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3.13. Main State Machine

The State Machine controls the overall behavior of the IC. Depending on the configuration data stored in the

E²PROM, the State Machine activates one of the different IC operational modes and controls the digital I/O

ports accordingly. In Slave Mode it processes the received master telegrams and computes the contents of

the slave answer, if required. Table 6 on page 6 lists all master calls that are decoded by the ASI4U in Slave

Mode.

To prevent the critical situation in which the IC gets locked in a not allowed state (i.e. by imission of strong

electromagnetic radiation) and thereby could jeopardize the entire system, all prohibited states of the state

machine will lead to an unconditioned logic reset which is comparable to the AS-i call ”Reset Slave (RES)”.

3.14. Communication Monitor/Watchdog

The IC contains an independent Communication Monitor that observes the processing of Data_Exchange and

Write_Parameter

requests. If no such requests have been processed for more than 40.960ms (+5%) the

Communication Monitor recognizes a No Data/Parameter Exchange status and turns the red status LED

(LED1) on. Any following Data_Exchange or Write_Parameter request will let the Communication Monitor start

over and turn the red status LED off.

The Communication Monitor is only activated at slave addresses unequal to zero (0) and while the IC is

processing the first Write_Parameter request after initialization. It becomes deactivated at any IC Reset or

after the reception of a Delete_Address Request.

If the Watchdog_Active flag (E²PROM Firmware Area) is set or the P0_Watchdog_Activation flag is set and

Parameter Port P0 is logic high, the Communication Monitor is switched to the so-called Watchdog Mode.

If the Communication Monitor detects a No Data/Parameter Exchange status in active Watchdog Mode, it

immediately invokes an unconditioned IC Reset, switching all Data and Parameter Outputs inactive,

generating corresponding Data and Parameter Strobe signals, setting the Data_Exchange_Disable flag and

starting the IC initialization procedure.

In order to resume to normal Data Port communication after a Watchdog IC Reset, the master has to send a

Write_Parameter

request again before Data Port communication can be reestablished. This ensures new

parameter setup of possibly connected external circuitry.

3.15. Toggle watchdog for 4I/4O processing in Extended Address Mode

As described in chapter 3.7.5 on page 6 a special 4I/4O data processing is supported in Extended Address

Mode. The transmission of a 4 bit wide output word is achieved by alternation of a high and a low nibble in

consecutive transactions. To ensure that both output nibbles become refreshed continuously by the Master,

the alternation of the I2 bit in the Data_Exchange call can be supervised by an I2 toggle watchdog in the IC.

The Toggle Watchdog is enabled at slave addresses unequal to zero (0) and while the IC is processing the

first data output event after initialization. It becomes disabled at any IC Reset or after the reception of a

Delete_Address

request.

The Toggle Watchdog function becomes activated only if the IC is operated in 4I/4O Mode (ID_code = 0xA,

Ext_Addr_4I/4O_Mode = ‘1’) and if either the Watchdog_Active flag is set in the E²PROM or the

P0_Watchdog_Activation

flag (also E²PROM) is set and Parameter Port P0 is logic HIGH.

If there is no alternation of bit I2 for 327ms (+16ms) at any time after the enable event, an activated Toggle

Watchdog invokes an unconditioned IC Reset, switching all Data and Parameter Outputs inactive, generating

corresponding Data and Parameter Strobe signals, setting the Data_Exchange_Disable flag and starting the

IC initialization procedure. Thus, the reaction of the IC is the same as for an expired Communication

Watchdog.

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