UPSD33XX Datasheet, PDF (48/231 Pages) STMicroelectronics – Fast 8032 MCU with Programmable Logic

uPSD33xx
POWER SAVING MODES
The uPSD33xx is a combination of two die, or
modules, each module having it’s own current
consumption characteristics. This section de-
scribes reduced power modes for the MCU Mod-
ule.
See
the
section,
Power
Management, page 137 for reduced power modes
of the PSD Module. Total current consumption for
the combined modules is determined in the DC
specifications at the end of this document.
The MCU Module has three software-selectable
modes of reduced power operation.
■ Idle Mode
■ Power-down Mode
■ Reduced Frequency Mode
Idle Mode
Idle Mode will halt the 8032 MCU core while leav-
ing the MCU peripherals active (Idle Mode blocks
MCU_CLK only). For lowest current consumption
in this mode, it is recommended to disable all un-
used peripherals, before entering Idle mode (such
as the ADC and the Debug Unit breakpoint com-
parators). The following functions remain fully ac-
tive during Idle Mode (except if disabled by SFR
settings).
■ External Interrupts INT0 and INT1
■ Timer 0, Timer 1 and Timer 2
■ Supervisor reset from: LVD, JTAG Debug,
External RESET_IN_, but not the WTD
■ ADC
■ I²C Interface
■ UART0 and UART1 Interfaces
■ SPI Interface
■ Programmable Counter Array
An interrupt generated by any of these peripher-
als, or a reset generated from the supervisor, will
cause Idle Mode to exit and the 8032 MCU will re-
sume normal operation.
The output state on I/O pins of MCU ports 1, 3, and
4 remain unchanged during Idle Mode.
To enter Idle Mode, the 8032 MCU executes an in-
struction to set the IDL bit in the SFR named
PCON, shown in Table 24., page 50. This is the
last instruction executed in normal operating mode
before Idle Mode is activated. Once in Idle Mode,
the MCU status is entirely preserved, and there
are no changes to: SP, PSW, PC, ACC, SFRs,
DATA, IDATA, or XDATA.
The following are factors related to Idle Mode exit:
– Activation of any enabled interrupt will cause
the IDL bit to be cleared by hardware,
terminating Idle Mode. The interrupt is
serviced, and following the Return from
Interrupt instruction (RETI), the next
instruction to be executed will be the one
which follows the instruction that set the IDL
bit in the PCON SFR.
– After a reset from the supervisor, the IDL bit is
cleared, Idle Mode is terminated, and the MCU
restarts after three MCU machine cycles.
Power-down Mode
Power-down Mode will halt the 8032 core and all
MCU peripherals (Power-down Mode blocks
MCU_CLK and PERIPH_CLK). This is the lowest
power state for the MCU Module. When the PSD
Module is also placed in Power-down mode, the
lowest total current consumption for the combined
die is achieved for the uPSD33xx. See Power
Management, page 137 in the PSD Module sec-
tion for details on how to also place the PSD Mod-
ule in Power-down mode. The sequence of 8032
instructions is important when placing both mod-
ules into Power-down Mode.
The instruction that sets the PD Bit in the SFR
named PCON (Table 24., page 50) is the last in-
struction executed prior to the MCU Module going
into Power-down Mode. Once in Power-down
Mode, the on-chip oscillator circuitry and all clocks
are stopped. The SFRs, DATA, IDATA,
and XDATA are preserved.
Power-down Mode is terminated only by a reset
from the supervisor, originating from the
RESET_IN_ pin, the Low-Voltage Detect circuit
(LVD), or a JTAG Debug reset command. Since
the clock to the WTD is not active during Power-
down mode, it is not possible for the supervisor to
generate a WDT reset.
Table 22., page 49 summarizes the status of I/O
pins and peripherals during Idle and Power-down
Modes on the MCU Module. Table 23., page 49
shows the state of 8032 MCU address, data, and
control signals during these modes.
Reduced Frequency Mode
The 8032 MCU consumes less current when oper-
ating at a lower clock frequency. The MCU can re-
duce it’s own clock frequency at run-time by
writing to three bits, CPUPS[2:0], in the SFR
named CCON0 described in Table 21., page 47.
These bits effectively divide the clock frequency
(f_OSC) coming in from the external crystal or oscil-
lator device. The clock division range is from 1/2 to
1/2048, and the resulting frequency is f_MCU.
This MCU clock division does not affect any of the
peripherals, except for the WTD. The clock driving
the WTD is the same clock driving the 8032 MCU
core as shown in Figure 14., page 46.
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