SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 133

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

7.7
The SAB 80C517 provides - due to Siemens ACMOS technology - three modes in which power
consumption can be significantly reduced.
All of these modes - a detailed description of each is given in the following sections - are entered
by software. Special function register PCON (power control register, see figure 7-57) is used to
select one of these modes.
These power saving modes, especially the power-down mode, replace the hardware power-down
supply for the internal RAM via a dedicated pin, as it is common with NMOS microcontrollers. During
the power saving modes, the power supply for the SAB 80C517 is again via all
no further dedicated pin for power-down supply.
For the SAB 80C517 several provisions have been made to quality it for both electrically noisy
environments and applications requiring high system security. In such applications unintentional
entering of the power saving modes must be absolutely avoided. A power saving mode would
reduce the controller’s performance (in the case of slow-down mode) or even stop any operation (in
the case of power-down mode). This situation might be fatal for the system, which is controlled by
the microcontroller. Such critical applications often use the watchdog timer to prevent the system
from program upsets. Then, an accidental entering of the power saving modes would even stop the
watchdog timer and would circumvent the watchdog timer’s task of system protection.
Semiconductor Group
– Idle mode
– Power-down mode
– Slow-down mode
The CPU is gated off from the oscillator. All peripherals are still provided with the clock and
are able to work.
Operation of the SAB 80C517 is completely stopped, the oscillator is turned off. This mode is
used to save the contents of the internal RAM with a very low standby current.
The controller keeps up the full operating functionality, but its normal clock frequency is
internally divided by eight. This slows down all parts of the controller, the CPU and all
peripherals, to 1/8th of their normal operating frequency. Slowing down the frequency greatly
reduces power consumption.
Power Saving Modes
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On-Chip Peripheral Components
V
CC
pins. There is