6 CLOCK MANAGEMENT UNIT (CMU)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
6-17
Oscillation Control Register (CMU_OSCCTL)
Register name Address
Bit
Name
Function
Setting
Init. R/W
Remarks
Oscillation
Control Register
(CMU_OSCCTL)
0x300101
(8 bits)
D7–4 OSC3WT[3:0] OSC3 wait cycle select
OSC3WT[3:0]
Wait cycle
0xf R/W Write-protected
0xf
0xe
0xd
0xc
0xb
0xa
0x9
0x8
0x7
0x6
0x5
0x4
0x3
0x2
0x1
0x0
128 cycles
256 cycles
512 cycles
1,024 cycles
2,048 cycles
4,096 cycles
8,192 cycles
16,384 cycles
32,768 cycles
65,536 cycles
131,072 cycles
262,144 cycles
524,288 cycles
1,048,576 cycles
2,097,152 cycles
4,194,304 cycles
D3–2 –
reserved
–
–
–
0 when being read.
D1
OSC1EN
OSC1 enable
1 Enable
0 Disable
1
R/W Write-protected
D0
OSC3EN
OSC3 enable
1 Enable
0 Disable
1
R/W
D[7:4]
OSC3WT[3:0]: OSC3 Wait Cycle Select Bits
An oscillation stabilization wait timer is set to prevent malfunctions due to unstable clock operation at
the start of OSC3 oscillation. The OSC3 or PLL clock is not supplied to the system immediately after
OSC3 oscillation starts—e.g., after an initial reset or when waking from SLEEP—until the time set here
has elapsed.
10.3 OSC3 Oscillation Stabilization Wait Time Settings
Table 6.
OSC3WT[3:0]
Oscillation stabilization wait time
0xf
128 cycles
0xe
256 cycles
0xd
512 cycles
0xc
1,024 cycles
0xb
2,048 cycles
0xa
4,096 cycles
0x9
8,192 cycles
0x8
16,384 cycles
0x7
32,768 cycles
0x6
65,536 cycles
0x5
131,072 cycles
0x4
262,144 cycles
0x3
524,288 cycles
0x2
1,048,576 cycles
0x1
2,097,152 cycles
0x0
4,194,304 cycles
(Default: 0xf)
This is set to 128 cycles (OSC3 clock) after an initial reset.
Notes: • The OSC3 oscillation stabilization wait timer cannot be used when the OSC3 oscillator is
turned on with software. Therefore, a software wait routine must be implemented.
• Oscillation stability will vary, depending on the resonator and other external components.
Carefully consider the OSC3 oscillation stabilization wait time before reducing the time.
When waking from SLEEP mode if OSC3 or PLL is used as the system clock source, set
the OSC3 oscillation stabilization wait time as follows:
OSC3 oscillation stabilization wait time [cycle]
≥
OSC3 oscillation start time [s] (max.)
×
f
SYSCLK
[Hz]
f
SYSCLK
: SYSCLK frequency when the clock source is OSC3 or PLL.
Example: When OSC3 oscillation start time (max.) = 10 ms and f
SYSCLK
= 48 MHz
OSC3 oscillation stabilization wait time
≥
480,000 [cycles]
OSC3WT[3:0] should be set to 0x3 (OSC3 oscillation stabilization wait time = 524,288
cycles).