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 instruction.

IDLE2

In IDLE2 power down mode (opcode = 06000001h), the 'C3x behaves as follows:

• No instructions are executed. Device in stand-by
• Power Consumption ‰50µA 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.

IDLE2 Timing

Interrupt response timing after IDLE2 operation

LOPOWER

In the LOPOWER (low power) mode, the 'C3x CPU behaves as follows:

 

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 instruction.

The LOPOWER instruction encoding (opcode) is 10800001h and the MAXSPEED instruction encoding is 10800000h.