sh66p51 SinoWealth Micro-Electronics Corp. Ltd, sh66p51 Datasheet - Page 15

• Manufacturer Part Number: sh66p51
• Description: Otp 2k 4-bit Micro-controller With Lcd Driver
• Manufacturer: SinoWealth Micro-Electronics Corp. Ltd

SH66P51
5.6. Programming Notes
It takes at least 5 ms for the OSCX oscillation circuit to turn on until the oscillation stabilizes. When switching the
CPU system clock from OSC to OSCX, the user must wait a minimum of 5ms since the OSCX oscillation is running.
However, the start time varies with respect to oscillator characteristics and the condition of use. Thus the wait time depends
on the application. When switching from OSCX to OSC, the user should switch clock first then turn off OSCX. If switching
from OSCX to OSC and turning off OSCX in one instruction, the OSCX turn off control will be delayed for one instruction
cycle automatically to prevent CPU operation error. Following is the timing of system clock switching.
OSCX turn off
OSCX turn on
OSCXO
OSCO
SYS CLOCK
High
Low frequency operation
High frequency operation
frequency
operation
Warm-up time
Switch from OSCX to OSC
Switch from OSC to OSCX
Figure 2. Timing of System Clock Switching
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