SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 135

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

Application Example for Switching Pin PE/SWD
For most applications in noisy environments, components external to the chip are used to give
warning of a power failure or a turn off of the power supply. These circuits could be used to control
the PE/SWD pin. The possible steps to go into power-down mode could then be as follows:
7.7.1
In idle mode the oscillator of the SAB 80C517 continues to run, but the CPU is gated off from the
clock signal. However, the interrupt system, the serial channels, the A/D converter, the oscillator
watchdog, the division/multiplication unit and all timers, except for the watchdog timer, are further
provided with the clock. The CPU status is preserved in its entirety: the stack pointer, program
counter, program status word, accumulator, and all other registers maintain their data during idle
mode.
The reduction of power consumption, which can be achieved by this feature, depends on the
number of peripherals running. lf all timers are stopped and the A/D converter and the division/
multiplication unit are not running, maximum power reduction can be achieved. This state is also
the test condition for the idle
Thus, the user has to take into account that the right peripheral continues to run or is stopped,
respectively, during idle. Also, the state of all port pins - either the pins controlled by their latches or
controlled by their secondary functions - depends on the status of the controller when entering idle.
Normally the port pins hold the logical state they had at the time idle was activated. lf some pins are
programmed to serve their alternate functions they still continue to output during idle if the assigned
function is on. This applies for the compare outputs as well as for the system clock output signal
and the serial interface in case the latter could not finish reception or transmission during normal
operation. The control signals ALE and PSEN are held at logic high levels (see table 7-13).
During idle, as in normal operating mode, the ports can be used as inputs. Thus, a capture or reload
operation as well as an A/D conversion can be triggered, the timers can be used to count external
events and external interrupts can be detected.
Semiconductor Group
– A power-fail signal forces the controller to go into a high priority interrupt routine. This interrupt
– Finally the controller enters power-down mode by executing the relevant double-instruction
routine saves the actual program status. At the same time pin PE/SWD is pulled low by the
power-fail signal.
sequence.
Idle Mode
I
CC
(see the DC characteristics in the data sheet).
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On-Chip Peripheral Components