Functional Description
2.6
Terminal Specific Functions
Watchdog and External Awake
In addition to the ISAC-S standard functions supporting the ISDN basic access, the ISAC-S
contains optional functions, useful in various terminal configurations.
The terminal specific functions are enabled by setting bit TSF (STCR register) to "1". This has
two effects:
– The SIP/EAW line is defined as an External Awake input (and not as SLD line);
– Second, the interrupts SAW and WOV (EXIR register) are enabled:
● SAW (Subscriber Awake) generated by a falling edge on the EAW line
● WOV (Watchdog timer overflow) generated by the watchdog timer. This occurs when the
processor fails to write two consecutive bit patterns in ADF1:
ADF1
WTC1
WTC2
Watchdog Timer Control 1, 0.
The WTC1 and WTC2 bits have to be successively written in the following manner within
128 ms:
WTC1
WTC2
1.
2.
1
0
0
1
As a result the watchdog timer is reset and restarted. Otherwise a WOV is generated.
Deactivating the terminal specific functions is only possible with a hardware reset.
Having enabled the terminal specific functions via TSF=1, the user can make the ISAC-S
generate a reset signal by programming the Reset Source Select RSS bit (CIXR/CIX0
register), as follows:
0 → A reset signal is generated as a result of
– a falling edge on the EAW line (subscriber awake)
– a C/I code change (exchange awake)
A falling edge on the EAW line also forces the IDP1 line of the IOM interface to zero.
The consequence of this is that the IOM interface and the ISAC-S leaves the
power-down state.
A corresponding interrupt status (CISQ or SAW) is also generated.
Semiconductor Group
104
INFINEON [ Infineon ]
