TMPR3901F

Chapter 5 Power-Down Mode

The TMPR3901F has the following four power-down modes to enable lower power dissipation through control of the internal clock.

Halt mode

Standby mode

Doze mode

Reduced Frequency mode

5.1Halt mode

Figure 5-1 shows a state diagram of power down mode.

 

 

 

 

 

 

 

Doze1

 

 

 

 

 

 

 

 

Doze

 

 

 

 

 

 

 

 

Active

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(Snoop enable)

 

 

 

 

 

 

 

 

 

 

 

 

Interrupt (RF=00)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Halt1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Interrupt(RF00)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RF00

 

 

RFnot 00

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Doze1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Interrupt(RF=00)

 

 

 

 

 

 

Standby

 

 

Halt

 

 

 

Halt1

 

Reduced frequency

 

(Snoop disable)

 

 

 

 

(1/2, 1/4, 1/8)

 

 

 

 

 

 

 

 

 

Interrupt(RF00)

Figure 5-1 State diagram of power-down mode

The TMPR3901F stops internal operations in Halt mode to reduce power dissipation. Setting the Config register Halt bit to 1 switches from Active mode to Halt mode. During Halt mode, the TMPR3901F will assert the HALT signal, stall the pipeline in ￿holding current￿status and cease to recognize bus requests.

If an instruction attempts to switch to Halt mode (by setting the Config register Halt bit to 1) during a bus operation, the HALT signal will not be asserted until completion of the bus operation. If a switch to Halt mode is attempted when a device other than the TMPR3901F owns the bus, the HALT signal will not be asserted until the TMPR3901F regains bus mastership. Write operations will continue even in Halt mode, if the write buffer contains data, until the buffer is emptied. SYSCLK and FCLK continue to run in Halt mode. The TMPR3901F can be returned from Halt mode to Active mode, and the Halt bit cleared to 0, by asserting the INT[5:0]*, NMI* or RESET* signals. The Status register IntMask field has no effect on the return to Active mode from Halt mode. The TMPR3901F will execute the corresponding exception handler for any unmasked INT[5:0]* interrupt as well as the RESET* and NMI* interrupts. When an INT[5:0]* signal is used to return to Active mode from Halt mode, and that signal's corresponding bit is masked in the IP field of the Status register, the TMPR3901F will resume execution of the instruction following the last instruction executed prior to entering Halt mode.

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Toshiba TX39 user manual Power-Down Mode, Halt mode