CHAPTER 5. PERIPHERAL HARDWARE FUNCTIONS

Fig. 5-11 Processor Clock Control Register Format

Address

3

2

1

0

 

 

 

 

 

 

 

 

 

FB3H

PCC3

PCC2

PCC1

PCC0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Symbol

PCC

CPU clock selection bits when fXX 4.19 MHz

 

 

( ) : When fXX = 4.19 MHz

 

 

 

 

 

 

 

CPU Clock Frequency

1 Machine Cycle

 

 

 

 

 

0

0

Φ Output = fXX/64 (65.5 kHz)

15.3

μs

 

 

 

 

 

0

1

Setting prohibited

 

 

 

 

 

 

1

0

Φ = fXX/8 (524 kHz)

19.1

μs

 

 

 

 

 

1

1

Φ = fXX/4 (1.05 MHz)

0.95

μs

 

 

 

 

 

When 4.19 MHz < fXX 5.0 MHz

 

 

 

 

( ) : When fXX = 4.19 MHz

 

 

 

 

 

 

 

 

 

 

 

 

CPU Clock Frequency

1 Machine Cycle

 

 

 

 

 

 

 

 

0

0

Φ Output = fXX/64 (76.7 kHz)

13 μs

 

 

 

 

 

 

 

 

 

0

1

Setting prohibited

 

 

 

 

 

 

 

 

 

 

1

0

Φ = fXX/8 (614 kHz)

1.63

μs

 

 

 

 

 

 

 

 

 

1

1

Setting prohibited

 

 

 

 

 

 

 

 

 

 

fXX : Main system clock oscillation circuit output frequency

 

 

 

CPU operating mode control bit

 

 

 

 

 

 

 

 

 

 

 

0

0

Normal operating mode

 

 

 

 

 

 

01 HALT mode

10 STOP mode

1 1 Setting prohibited

Note When using a calue of fXX such that 4.19 MHz < fXX 5.0 MHz, if maximum speed mode : Φ fXX/4 (PCC1, PCC0

=11) is set as CPU clock frequency, 1 machine cycle is less than 0.95 μs and the standard minimum value 0.95 μs is not kept.

Therefore, is this case, PCC1, PCC0 = 11 cannot be set, so it should be used with PCC1, PCC0 = 00 or 10.

As a result, the combination of “fXX = 4.19 MHz, PCC1, PCC0 = 11” is maximum speed selection (1 machin cycle = 0.95 μs) as CPU clock.

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Image 67
NEC PD75402A, PD75P402 user manual FB3H PCC3 PCC2 PCC1 PCC0, Pcc