Low Power Modes
The TMS320C3x CPU has been enhanced by the addition of two
power management modes, IDLE2 and LOPOWER. Either
mode is invoked by executing the corresponding power-down
In IDLE2 power down mode (opcode = 06000001h), the 'C3x
behaves as follows:
- No instructions are executed. Device in stand-by
- Power Consumption 50ľA with CLKIN shut off
- The CPU, peripherals, and internal memory will retain
their previous state.
- The external bus output pins are idle:
- address lines remain in their previous state
- data lines are in the high impedance state
- output control signals are inactive
- Clocks will stop with H1 high and H3 low, when the device
is in the functional (non-emulation) mode.
- When the device is in emulation mode and the IDLE2
instruction is executed, the H1 and H3 clocks
continue to operate normally and the CPU behaves
as if an IDLE instruction had been
executed. The clocks continue to run for correct
operation of the emulator.
- Wake-up by external interrupt (/INT0-/INT3) is asserted
for at least two H1 cycles.
- When one of the four interrupts is asserted, the
clocks start after a delay of one H1 cycle. The
clocks can start up in the phase opposite to that
in which they were stopped (i.e., H1 may start
low when H3 was low before stopping the clocks
and H3 may start low when H1 was previously low).
However, the H1 and H3 clocks will remain 180
degrees out of phase with each other.
- To avoid generating multiple false interrupts in
level trigger mode, the interrupt must be
asserted for less than three H1 cycles.
- The interrupt service routine must have been setup before
placing device in IDLE2 mode since the instruction
following the IDLE2 instruction will not be
executed until the RETI (return from interrupt)
instruction is executed.
Note: For correct device operation, the
three instructions following a delayed branch should not include
either IDLE or IDLE2 instructions.
Interrupt response timing after IDLE2
In the LOPOWER (low power) mode, the 'C3x CPU behaves
- CPU executes at CLKIN/16 rate
- For example, a TMS320C3x with a CLKIN frequency of 32
MHz will perform the same as a 2 MHz TMS320C3x, which
has an instruction cycle time of 1000 ns or 1 MHz).
- Power Consumption ~ 1/5 ICC
- MAXSPEED brings CPU to full speed
The TMS320C3x slows down to 1/16 of full speed operation
during the read phase of the LOPOWER instruction. The TMS320C3x
resumes full speed operation during the read phase of the MAXSPEED
The LOPOWER instruction encoding (opcode) is 10800001h
and the MAXSPEED instruction encoding is 10800000h.