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XC2200 Derivatives
System Units (Vol. 1 of 2)
System Control Unit (SCU)
User’s Manual
6-71
V2.1, 2008-08
SCU, V1.13
6.4.1.1
ESR as Reset Input
The pins ESRx can serve as an external reset input as well as a reset output (open drain)
for Internal Application and Application Resets. Additionally several GPIO pad triggers
that can be enabled additionally via register ESREXCONx interfere with the ESR pin
function. GPIO and ESR pin triggers can be enabled/disabled individually and are
combined for the reset trigger generation. For more information about the reset system
see
.
Note: The reset output is only asserted for the duration the reset counter RSTCNTA is
active. During a possible reset extension the reset output is not longer asserted.
6.4.1.2
ESR as Reset Output
If pin ESRx is enabled as reset output and the input level is low while the output stage is
disabled (indicating that it is still driven low externally), the reset circuitry holds the chip
in reset until a high level is detected on ESRx. The internal output stage drives a low level
during reset only while RSTCNTA is active. It deactivates the output stage when the time
defined by RSTCNTCON.RELA has passed. For more information about the reset
system see
.
6.4.1.3
ESR as Trap Trigger
The ESR can request traps. The control mechanism if and which trap is requested is
located in the trap control logic. For more information see
6.4.1.4
ESR as Wake-up Trigger for the PSC
When the device is currently in a power save state the ESR pin can be used as a wake-
up trigger.
For the ESR trigger configuration the following options are available:
•
Share ESR1 and ESR2 with serial IO function(s)
For information which other peripheral input signal is on an ESR overlay pin see
.
• Select active edge(s)
• Enable / disable filter
• Control other ESR functions
For more information see
and the Programmer’s Guide.
Note: The Asynchronous Edge Detection (ESRCFGx.AEDCON) needs special care in
case of a parallel clock-off switching and an external wake-up. A wake-up trigger
before the clock is switched off will not be recognized. Any wake-up trigger
occuring after the clock has been switched off will wake-up the device in any case.
A wake-up pulse of 1 ms or at least two wake-up pulses within a time period of
1 ms ensure a wake-up.