sh66k51a SinoWealth Micro-Electronics Corp. Ltd, sh66k51a Datasheet - Page 15

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

5.5. Control of Oscillator
The configuration of the oscillator control register is shown as follows.
OXON: OSCX oscillation on/off.
OXM: switching system clock.
OXS: OSCX oscillator type selection
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.
Address
$14
0: Turn-off OSCX oscillation
0: select OSC as system clock
0: OSCX set as ceramic oscillator
SYS CLOCK
OXS
Bit3
OSCXO
OSCO
Bit2
-
frequency
operation
High
OXM
Bit1
Switch from OSCX to OSC
Timing of System Clock Switching
OXON
Bit0
OSCX turn off
Low frequency operation
1: Turn-on OSCX oscillation
1: select OSCX as system clock
1: OSCX set as RC oscillator, and set OSCXI/OSCXO as PORTE
R/W
R/W
15
Bit0: Turn on OSCX oscillator
Bit1: CPU clocks select (1: OSCX/0: OSC)
Bit3: OSCX type selection
OSCX turn on
Warm-up time
Remarks
Switch from OSC to OSCX
High frequency operation
SH66K51A