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Semiconductor Group
101
On-Chip Peripheral Components
7.6.2.1 Power-Down Mode of the SAB 80C515/80C535
In the power-down mode, the on-chip oscillator is stopped. Therefore, all functions are stopped,
only the contents of the on-chip RAM and the SFR’s are held. The port pins controlled by their port
latches output the values that are held by their SFR’S. The port pins which serve the alternate
output functions show the values they had at the end of the last cycle of the instruction which
initiated the power-down mode; when enabled, the clockout signal (P1.6/CLKOUT) will stop at low
level. ALE and PSEN are held at logic low level (see table 7-10).
lf the power-down mode is to be used, the pin PE must be held low. Entering the power-down mode
is done by two consecutive instructions immediately following each other. The first instruction has
to set the flag bit PDE (PCON.1) and must not set bit PDS (PCON.6). The following instruction has
to set the start bit PDS (PCON.6) and must not set bit PDE (PCON.1). The hardware ensures that
a concurrent setting of both bits, PDE and PDS, will not initiate the power-down mode. Bit PDE and
PDS will automatically be cleared after having been set and the value shown when reading one of
these bits is always zero (0). Figure 7-44 shows the special function register PCON. This double-
instruction sequence is implemented to minimize the chance of unintentionall entering the power-
down mode, which could possibly "freeze" the chip’s activity in an undesired status.
Note that PCON is not a bit-addressable register, so the above mentioned sequence for entering
the power-down mode is composed of byte handling instructions.
The following instruction sequence may serve as an example:
ORL
PCON,#00000010B
;Set bit PDE,
;bit PDS must not be set
ORL
PCON,#01000000B
;Set bit PDS,
;bit PDE must not be set
The instruction that sets bit PDS is the last instruction executed before going into power-down
mode. lf idle mode and power-down mode are invoked simultaneously, the power-down mode takes
precedence.
The only exit from power-down mode is a hardware reset. Reset will redefine all SFR’S, but will not
change the contents of the internal RAM.
In the power-down mode,
V
CC
can be reduced to minimize power consumption. Care must be taken,
however, to ensure that
V
CC
is not reduced before the power-down mode is invoked, and that
V
CC
is restored to its normal operating level before the power-down mode is terminated. The reset signal
that terminates the power-down mode also frees the oscillator. The reset should not be activated
before
V
CC
is restored to its normal operating level and must be held active long enough to allow the
oscillator to restart and stabilize (similar to power-on reset).
*
Summary of Contents for SAB 80515 Series
Page 9: ...Semiconductor Group 9 Introduction Figure 1 2 Block Diagram ...
Page 12: ...Semiconductor Group 12 Fundamental Structure Figure 2 1 Detailed Block Diagram ...
Page 18: ...Semiconductor Group 18 Central Processing Unit Figure 3 1 Fetch Execute Sequence ...
Page 73: ...Semiconductor Group 73 On Chip Peripheral Components Figure 7 25 A D Converter Block Diagram ...
Page 83: ...Semiconductor Group 83 On Chip Peripheral Components Figure 7 33 a Timer 2 Block Diagram ...
Page 215: ...Device Specifications Semiconductor Group 215 ...
Page 217: ...Device Specifications Semiconductor Group 217 Pin Configuration P LCC 68 ...
Page 219: ...Device Specifications Semiconductor Group 219 Logic Symbol ...
Page 226: ...Device Specifications Semiconductor Group 226 Figure 1 Block Diagram ...
Page 229: ...Device Specifications Semiconductor Group 229 Figure 2 Memory Address Spaces ...
Page 239: ...Device Specifications Semiconductor Group 239 Figure 4 Block Diagram of the A D Converter ...
Page 241: ...Device Specifications Semiconductor Group 241 Figure 5 Interrupt Request Sources ...
Page 242: ...Device Specifications Semiconductor Group 242 Figure 6 Interrupt Priority Level Structure ...