UPD75238GJ NEC [NEC], UPD75238GJ Datasheet - Page 49

• Manufacturer Part Number: UPD75238GJ
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC [NEC]

4.2 CLOCK GENERATOR
(1) Configuration of the clock generator
The clock generator supplies various clock signals to the CPU and peripheral hardware. Fig. 4-14 shows
the configuration of the clock generator.
Note Instruction execution
Remarks 1. f
HALT
STOP
4
Note
Note
PCC2, PCC3
clear signal
SCC3
SCC0
PCC0
PCC1
PCC2
PCC3
2. f
3.
4. PCC : Processor clock control register
5. SCC: System clock control register
6. One clock cycle (t
SCC
PCC
XT1
XT2
X1
X2
Chapter 11 for details of t
X
XT
: Main system clock frequency
: Subsystem clock frequency
= CPU clock
Subsystem
clock generator
Main system
clock generator
Oscillator
disable
signal
Fig. 4-14 Block Diagram of the Clock Generator
STOP F/F
Q
CY
) of the CPU clock ( ) is equal to one machine cycle of an instruction. See
f
f
XT
X
R
S
CY
Clock timer
.
Timer/pulse
generator
1/2
1/4
1/16
Selec-
tor
Frequency divider
1/8 to 1/4096
HALT F/F
R
S
Selec-
tor
Q
•
•
•
•
•
•
•
Wait release signal from BT
Standby release signal from
interrupt control circuit
FIP controller/driver
Basic interval timer (BT)
Timer/event counter
Serial interface
Clock timer
Clock output circuit
INT0 voice eliminator
RESET signal
Frequency
divider
1/4
PD75238
•
•
•
eliminator
circuit
CPU
INT0 noise
Clock output
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