SAB80C515A-5 Datasheet, PDF (88/108 Pages) Siemens Semiconductor Group – 8-Bit CMOS Single-Chip Microcontroller Family

SAB 80C515A/83C515A-5
Software Power Down Mode
The power down mode is entered by two consecutive instructions directly following each other.
The first instruction has to set the flag PDE (power down enable) and must not set PDS (power
down set). The following instruction has to set the start bit PDS. Bits PDE and PDS will
automatically be cleared after having been set.
The instruction that sets bit PDS is the last instruction executed before going into power down
mode. The only exit from power down mode is a hardware reset.
The status of all output lines of the controller can be looked up in table 5.
Hardware Controlled Power Down Mode
The pin HWPD controls this mode. If it is on logic high level (inactive) the part is running in the
normal operating modes. If pin HWPD gets active (low level) the part enters the Hardware
Power Down Mode; this is independent of the state of pin PE/SWD.
HWPD is sampled once per machine cycle. If it is found active, the device starts a complete
internal reset sequence. The watchdog timer is stopped and its status flag WDTS is cleared
exactly the same effects as a hardware reset. In this phase the power consumption is not yet
reduced. After completion of the internal reset both oscillators of the chip are disabled. At the
same time the port pins and several control lines enter a floating state as shown in table 5. In
this state the power consumption is reduced to the power down current IPD. Also the supply
voltage can be reduced. Table 5 also lists the voltages which may be applied at the pins during
Hardware Power Down Mode without affecting the low power consumption.
Termination of HWPD Mode:
This power down state is maintained while pin HWPD is held active. If HWPD goes to high
level (inactive state) an automatic start up procedure is performed:
– First the pins leave their floating condition and enter their default reset state (as they had
immediately before going to float state).
– Both oscillators are enabled. The oscillator watchdog’s RC oscillator starts up very fast (typ.
less than 2 ms).
– Because the oscillator watchdog is active it detects a failure condition if the on-chip oscillator
hasn’t yet started. Hence, the watchdog keeps the part in reset and supplies the internal
clock from the RC oscillator.
– Finally, when the on-chip oscillator has started, the oscillator watchdog releases the part
from reset with oscillator watchdog status flag set.
When automatic start of the watchdog was enabled (PE/SWD connected to V_CC), the
Watchdog Timer will start, too (with its default reload value for time-out period).
– The Reset pin overrides the Hardware Power Down function, i.e. if reset gets active during
Hardware Power Down it is terminated and the device performs the normal
resetfunction.(Thus, pin Reset has to be inactive during Hardware Power Down Mode).
function.(Thus, pin Reset has to be inactive during Hardware Power Down Mode).
Semiconductor Group
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