sh66k51a SinoWealth Micro-Electronics Corp. Ltd, sh66k51a Datasheet - Page 13

• Manufacturer Part Number: sh66k51a
• Description: 2k 4-bit Micro-controller With Lcd Driver
• Manufacturer: SinoWealth Micro-Electronics Corp. Ltd

5. System Clock and Oscillator
The oscillator generates the basic clock pulses that provide the system clock to supply CPU and on-chip peripherals.
System clock = f
5.1. Instruction Cycle Time:
(1) 4/32.768kHz (≈122.07µs) for 32.768kHz oscillator
(2) 4/131kHz (≈30.52µs) for 131kHz oscillator
(3) 4/455kHz (≈ 8.79µs) for 455kHz oscillator
(4) 4/4MHz (= 1µs) for 4MHz oscillator
5.2. Circuit Configuration
SH66K51A has two on-chip oscillation circuits OSC and OSCX.
OSC is a low frequency crystal (Typ. 32.768kHz) or RC (Typ. 131kHz) determined by the Code Option. This is designed for
low frequency operation. OSCX also has two types: ceramic/crystal (Typ. 4MHz) or internal RC (4MHz ± 2%) determined by
system register. It is designed for high frequency operation.
It is possible to select the high speed CPU processing by a high frequency clock and select low power operation by low
operation clock. At starting of reset initialization, OSC starts oscillation and OSCX is turned off. Immediately after reset
initialization, the OSC clock is automatically selected as the system clock input source.
5.3. OSC Oscillation
The OSC generates the basic clock pulses that provide the CPU and peripherals (Base timer, LCD) with an operating clock.
(1) OSC Crystal Oscillator
(2) OSC RC Oscillator
OSC
External RC
/4
OSCXO
OSCXI
OSCO
OSCO
OSCI
OSCI
OSCI
High Frequency
Clock Oscillator
Clock Oscillator
Low Frequency
1000pF
R
OSC
Oscillator Block Diagram
Crystal
C1
C2
V
DD
& Switching control
Source Selector
System clock
13
System clock
Generator
CPU Clock
SH66K51A