SAB80515 Datasheet, PDF (99/270 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller Family

On-Chip Peripheral Components
7.6.1 Power Saving Modes of the SAB 80515/80535
The SAB 80515/80535 allows a reduction of the power consumption using the power-down mode.
7.6.1.1 Power-Down Mode of the SAB 80515/80535
The power-down mode in the SAB 80515/80535 allows a reduction of V_CC , to zero while saving 40
bytes of the on-chip RAM through a backup supply connected to the V_PD pin. In the following, the
terms V_CC and V_PD are used to specify the voltages on pin V_CC and pin V_PD, respectively.
lf V_CC > V_PD , the 40 bytes are supplied from V_CC . V_PD may then below. lf V_CC < V_PD , the current for
the 40 bytes is drawn from V_PD . The addresses of these backup-powered RAM locations range from
88 to 127 (58H to 7FH). The current drawn from the backup power supply is typically 1 mA, max. 3
mA.
To utilize this feature, the user’s system - upon detecting an imminent power failure - would interrupt
the processor in some manner to transfer relevant data to the 40-byte on-chip RAM and enable the
backup power supply to the V_PD pin. Then a reset should be accomplished before V_CC falls below
its operating limit. When power returns, a power-on reset should be accomplished, and the backup
supply needs to stay on long enough to resume normal operation. Figure 7-43 illustrates the timing
upon a power failure.
Figure 7-43
Reset and RAM Backup Power Timing of the SAB 80515/80535
Semiconductor Group
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