ASI4U datasheet(41/64 Pages) ETC2

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ASI4U / ASI4U-E / ASI4U-F

Spec. 3.0 Compliant Universal AS-I IC

Data Sheet

April 2, 2012

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became accidentally deactivated by a hardware fault, an exchange of the bits would be recognized

after 4 cycles in a running application (see Figure 14).



Inverter at the data inputs

In Safety Mode it is still possible to use the Data Input Invert functionality (either joint input inverting or

bit selective input inverting) of the IC. This allows to transform the default signal level of the external

application (either High or Low) to the required default input level for AS-I Safety. For safety

considerations there is no difference whether the inverter is integrated in the ASI4U IC or added

externally. An error in the inverter or inverter activation will be recognized by a running application

within the next cycle.

The following feature descriptions relate to the logical signals after the (optional) data input inverters.

Important Note: As described above, the pin assignment of DI2 and DI3 is exchanged in Safety

Mode. However, the configuration register for selective input inverting is directly

associated with the physical IC ports and is not changed. Thus, in Safety Mode Bit3

of the DI_Invert_Configuration register defines the inverting of the logical signal DI2

and Bit2 defines the inverting the signal DI3.



Modification of Code Sequence

The transmitted value for D0 is calculated according to the following equation:

D0 = D0 XOR (D1 AND D2 AND D3)

Thus, the ASI4U will generate ‘1110’ from the input value ‘1111’ and ‘1111’ from the input value

‘1110’. To comply with the coding rules of the safe AS-i communication, which prohibit ‘1111’ as a

valid state in the data stream, the external code generator has to store ‘1111’ instead of ‘1110’.

In case the Safety Mode became accidentally deactivated by an hardware fault, the IC would not

perform the D0 combination anymore. The Safety Monitor would notice this as an error by reception of

‘1111’, see Figure 15.



Deactivation of the standard data path

Theoretically, the Safety Mode could become deactivated for a single bit only, if a (single) fault occurs

at one of the multiplexers. This would lead to code sequences where three bits are routed in the

Safety Path and the fourth bit is routed in the Standard Path. Therefore, an additional OR-Gate is

added in the Standard Path, that ties the Standard Path to constant ‘1’ once the Safety Mode is

activated.

A valid data transfer in Standard Mode or Safety Mode is only possible, if all four multiplexers are

switched to the same direction. Any other state will be recognized by the Safety Monitor.



Activation of Data_Exchange_Disable

The Data_Exchange_Disable flag is set by the IC after Reset and will be cleared after the first

Parameter call. As long as the flag is set, the IC does not respond to Data_Exchange calls. In case

the Safety Mode is activated and the Synchronous_Data_IO flag or any of the DI_Filter_Configuration

flags are set in the Firmware Area of the E²PROM, the Data_Exchange_Disable flag cannot be

cleared. This prevents any data communication in that particular case. See Figure 16.

Following flow charts are valid in Safety Mode of the ASI4U:

Note:

>=1

represents a logical OR

represents a logical XOR

represents a logical AND

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