SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 134

• Manufacturer Part Number: SAB80C517-M16
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Hardware Enable for the Use of the Power Saving Modes
To provide power saving modes together with effective protection against unintentional entering of
these modes, the SAB 80C517 has an extra pin disabling the use of the power saving modes. As
this pin will most likely be used only in critical applications it is combined with an automatic start of
the watchdog timer (see the description in section 7.8 "Fail Save Mechanisms"). This pin is called
PE/SWD (powers saving enable/start watchdog timer) and its function is as follows:
PE/SWD = 1 (logic high level)
PE/SWD = 0 (logic low level)
When left unconnected, the pin PE/SWD is pulled to high level by a weak internal pullup. This is
done to provide system protection by default.
The logic level applied to pin PE/SWD can be changed during program execution in order to allow
or block the use of the power saving modes without any effect on the on-chip watchdog circuitry;
(the watchdog timer is started only if PE/SWD is on high level at the moment when reset is released;
a change at PE/SWD during program execution has no effect on the watchdog timer; this only
enables or disables the use of the power saving modes.). A change of the pin’s level is detected in
state 3, phase 1. A Schmitt trigger is used at the input to reduce susceptibility to noise.
In addition to the hardware enable/disable of the power saving modes, a double-instruction
sequence which is described in the corresponding sections is necessary to enter power-down and
idle mode. The combination of all these safety precautions provide a maximum of system
protection.
Semiconductor Group
– Use of the power saving modes is not possible. The instruction sequences used for entering
– lf and only if PE/SWD is held at high level during reset, the watchdog timer is started
– All power saving modes can be activated as described in the following sections
– The watchdog timer has to be started by software if system protection is desired.
these modes will not affect the normal operation of the device.
immediately after reset is released.
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On-Chip Peripheral Components