psd813f3 STMicroelectronics, psd813f3 Datasheet - Page 62

• Manufacturer Part Number: psd813f3
• Description: Flash In-system Programmable Isp Peripherals For 8-bit Mcus
• Manufacturer: STMicroelectronics

PSD813F2, PSD833F2, PSD834F2, PSD853F2, PSD854F2
POWER MANAGEMENT
All PSD devices offer configurable power saving
options. These options may be used individually or
in combinations, as follows:
62/110
The PLD sections can also achieve Stand-by
mode when its inputs are not changing, as
described in the sections on the Power
Management Mode Registers (PMMR).
Built in logic monitors the Address Strobe of the
MCU for activity. If there is no activity for a
certain time period (MCU is asleep), the APD
Unit initiates Power-down mode (if enabled).
Once in Power-down mode, all address/data
signals are blocked from reaching PSD memory
and PLDs, and the memories are deselected
internally. This allows the memory and PLDs to
All memory blocks in a PSD (primary and
secondary Flash memory, and SRAM) are
built with power management technology. In
addition to using special silicon design
methodology, power management technology
puts the memories into standby mode when
address/data inputs are not changing (zero
DC current). As soon as a transition occurs on
an input, the affected memory “wakes up”,
changes and latches its outputs, then goes
back to standby. The designer does not have
to do anything special to achieve memory
standby mode when no inputs are changing—
it happens automatically.
As with the Power Management mode, the
Automatic Power Down (APD) block allows
the PSD to reduce to stand-by current
automatically. The APD Unit can also block
MCU address/data signals from reaching the
memories and PLDs. This feature is available
on all the devices of the PSD family. The APD
Unit is described in more detail in the sections
entitled
and Power-down Mode, page
Automatic Power-down (APD) Unit
63.
remain in standby mode even if the address/
data signals are changing state externally
(noise, other devices on the MCU bus, etc.).
Keep in mind that any unblocked PLD input
signals that are changing states keeps the PLD
out of Stand-by mode, but not the memories.
PSD devices have a Turbo Bit in PMMR0. This
bit can be set to turn the Turbo mode off (the
default is with Turbo mode turned on). While
Turbo mode is off, the PLDs can achieve
standby current when no PLD inputs are
changing (zero DC current). Even when inputs
do change, significant power can be saved at
lower frequencies (AC current), compared to
when Turbo mode is on. When the Turbo mode
is on, there is a significant DC current
component and the AC component is higher.
PSD Chip Select Input (CSI, PD2) can be
used to disable the internal memories, placing
them in standby mode even if inputs are
changing. This feature does not block any
internal signals or disable the PLDs. This is a
good alternative to using the APD Unit. There
is a slight penalty in memory access time
when PSD Chip Select Input (CSI, PD2)
makes its initial transition from deselected to
selected.
The PMMRs can be written by the MCU at run-
time to manage power. All PSD supports
“blocking bits” in these registers that are set to
block designated signals from reaching both
PLDs. Current consumption of the PLDs is
directly related to the composite frequency of
the changes on their inputs (see Figure
Figure 36., page
savings can be achieved by blocking signals
that are not used in DPLD or CPLD logic
equations.
72). Significant power
35
and