UPD75238GJ

Manufacturer Part NumberUPD75238GJ
Description4 BIT SINGLE-CHIP MICROCOMPUTER
ManufacturerNEC [NEC]
UPD75238GJ datasheet
 
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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.
Fig. 4-14 Block Diagram of the Clock Generator
XT1
f
Subsystem
XT
clock generator
XT2
X1
f
Main system
X
clock generator
X2
Oscillator
disable
SCC
signal
SCC3
SCC0
PCC
PCC0
PCC1
4
PCC2
Note
HALT
PCC3
Note
STOP
PCC2, PCC3
clear signal
STOP F/F
Q
Note Instruction execution
Remarks 1. f
: Main system clock frequency
X
2. f
: Subsystem clock frequency
XT
3.
= CPU clock
4. PCC : Processor clock control register
5. SCC: System clock control register
6. One clock cycle (t
) of the CPU clock ( ) is equal to one machine cycle of an instruction. See
CY
Chapter 11 for details of t
Clock timer
Timer/pulse
generator
1/8 to 1/4096
Frequency divider
1/2
1/4
1/16
Selec-
tor
Selec-
tor
HALT F/F
S
R
S
R
.
CY
PD75238
FIP controller/driver
Basic interval timer (BT)
Timer/event counter
Serial interface
Clock timer
Clock output circuit
INT0 voice eliminator
Frequency
divider
1/4
CPU
INT0 noise
eliminator
Clock output
circuit
Q
Wait release signal from BT
RESET signal
Standby release signal from
interrupt control circuit
49