IBM uPD78082 - Manual (Page 100)

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CHAPTER 5 CLOCK GENERATOR
5.6 Changing CPU Clock Settings
5.6.1 Time required for CPU clock switchover
The CPU clock can be switched over by means of bits 0 to 2 (PCC0 to PCC2) of the processor clock control register
(PCC).
The actual switchover operation is not performed directly after writing to the PCC, but operation continues on the
pre-switchover clock for several instructions (see Table 5-2).
Table 5-2. Maximum Time Required for CPU Clock Switchover
1 0 0 1 1 0 1 0 0 1 0 0 0 0 0
PCC0 PCC2 PCC1
0
0 0
0 1 1
0 0
0
1
1
1 8 instructions
2 instructions
4 instructions 4 instructions
2 instructions
8 instructions
4 instructions 4 instructions
2 instructions
8 instructions 8 instructions
2 instructions
Set Values After Switchover Set Values before
Switchover
1 instruction 1 instruction 1 instruction
PCC1 PCC2 PCC0 PCC1 PCC2 PCC0 PCC1 PCC2 PCC0 PCC1 PCC2 PCC0 PCC1 PCC2 PCC0
1 instruction
Remark One instruction is the minimum instruction execution time with the pre-switchover CPU clock.
0 0 0 16 instructions 16 instructions 16 instructions 16 instructions