Intermittent Cpu Operation Function - Fujitsu F2MC-16LX Hardware Manual

CHAPTER 5 LOW-POWER CONSUMPTION CONTROL CIRCUIT
5.5

Intermittent CPU Operation Function

The intermittent CPU operation function stops the clock supplied to the CPU for the
specified time and delays the start of the internal bus cycle in the following case:
• When registers, internal memory (ROM, RAM, I/O, and resources), and the external
bus are accessed
■ Intermittent CPU Operation Function
The intermittent CPU operation function can be used to perform processing with low-power
consumption because the CPU execution speed is lowered by supplying the internal resources
with a high-speed clock. Use the CG1 and CG0 bits to select the temporary stop cycle count for
the clock supplied to the CPU.
The external bus operation itself is performed using the same clock as the resources.
The execution time required when the intermittent CPU operation function is used can be
obtained as follows:
• Add to the normal execution time the compensation value obtained by multiplying the
number of accesses to registers, internal memory, internal resources, and the external bus
by the temporary stop cycle count.
Resources
clock
CPU clock
108
Figure 5.5-1 Intermittent CPU Operation
Temporary stop cycles during
intermittent operation
Internal bus start cycle