56F8335 datasheet(116/160 Pages) FREESCALE

116 / 160 page

56F8335 Technical Data, Rev. 5

116

Freescale Semiconductor

Preliminary

6.8 Stop and Wait Mode Disable Function

Figure 6-16 Internal Stop Disable Circuit

The 56800E core contains both STOP and WAIT instructions. Both put the CPU to sleep. For lowest

power consumption in Stop mode, the PLL can be shut down. This must be done explicitly before entering

Stop mode, since there is no automatic mechanism for this. When the PLL is shut down, the 56800E

system clock must be set equal to the oscillator output.

Some applications require the 56800E STOP and WAIT instructions to be disabled. To disable those

instructions, write to the SIM control register (SIM_CONTROL), described in Part 6.5.1. This procedure

can be on either a permanent or temporary basis. Permanently assigned applications last only until their

next reset.

6.9 Resets

The SIM supports four sources of reset. The two asynchronous sources are the external RESET pin and

the Power-On Reset (POR). The two synchronous sources are the software reset, which is generated within

the SIM itself by writing to the SIM_CONTROL register, and the COP reset.

Reset begins with the assertion of any of the reset sources. Release of reset to various blocks is sequenced

to permit proper operation of the device. A POR reset is first extended for 221 clock cycles to permit

stabilization of the clock source, followed by a 32 clock window in which SIM clocking is initiated. It is

then followed by a 32 clock window in which peripherals are released to implement Flash security, and,

finally, followed by a 32 clock window in which the core is initialized. After completion of the described

reset sequence, application code will begin execution.

Resets may be asserted asynchronously, but are always released internally on a rising edge of the system

clock.

D-FLOP

56800E

STOP_DIS

Permanent

Disable

Reprogrammable

Disable

Clock

Select

Reset

Note: Wait disable circuit is similar

56F8335 Datasheet(PDF) 116 Page - Freescale Semiconductor, Inc