2 POWER SUPPLY, RESET, AND CLOCKS
S1C17M20/M21/M22/M23/M24/M25
Seiko Epson Corporation
2-15
TECHNICAL MANUAL (Rev. 1.0)
CLG System Clock Control Register
Register name
Bit
Bit name
Initial
Reset
R/W
Remarks
CLGSCLK
15 WUPMD
0
H0
R/WP –
14 –
0
–
R
13–12 WUPDIV[1:0]
0x0
H0
R/WP
11–10 –
0x0
–
R
9–8 WUPSRC[1:0]
0x0
H0
R/WP
7–6 –
0x0
–
R
5–4 CLKDIV[1:0]
0x0
H0
R/WP
3–2 –
0x0
–
R
1–0 CLKSRC[1:0]
0x0
H0
R/WP
Bit 15
WUPMD
This bit enables the SYSCLK switching function at wake-up.
1 (R/WP): Enable
0 (R/WP): Disable
When the CLGSCLK.WUPMD bit = 1, setting values of the CLGSCLK.WUPSRC[1:0] bits and the
CLGSCLK.WUPDIV[1:0] bits are loaded to the CLGSCLK.CLKSRC[1:0] bits and the CLGSCLK.
CLKDIV[1:0] bits, respectively, at wake-up from SLEEP mode to switch SYSCLK. When the CLG-
SCLK.WUPMD bit = 0, the CLGSCLK.CLKSRC[1:0] and CLGSCLK.CLKDIV[1:0] bits are not
altered at wake-up.
Note
: When the CLGSCLK.WUPMD bit = 1, the clock source enable bits (CLGOSC.EXOSCEN,
CLGOSC.OSC1EN, CLGOSC.OSC3EN, CLGOSC.IOSCEN) except for the SYSCLK source
selected by the CLGSCLK.CLKSRC[1:0] bits will be cleared to 0 to stop the clocks after a
system wake-up. However, the enable bit of the clock source being operated during SLEEP
mode by setting the CLGOSC.
****
SLPC bit retains 1 after a wake-up.
Bit 14
Reserved
Bits 13–12 WUPDIV[1:0]
These bits select the SYSCLK division ratio for resetting the CLGSCLK.CLKDIV[1:0] bits at wake-up.
This setting is ineffective when the CLGSCLK.WUPMD bit = 0.
Bits 11–10 Reserved
Bits 9–8
WUPSRC[1:0]
These bits select the SYSCLK clock source for resetting the CLGSCLK.CLKSRC[1:0] bits at wake-up.
When a currently stopped clock source is selected, it will automatically start oscillating or clock input
at wake-up. However, this setting is ineffective when the CLGSCLK.WUPMD bit = 0.
Table 2.6.2 SYSCLK Clock Source and Division Ratio Settings at Wake-up
CLGSCLK.
WUPDIV[1:0] bits
CLGSCLK.WUPSRC[1:0] bits
0x0
0x1
0x2
0x3
IOSCCLK
OSC1CLK
OSC3CLK
EXOSCCLK
0x3
1/8
Reserved
1/8
Reserved
0x2
1/4
Reserved
1/4
Reserved
0x1
1/2
1/2
1/2
Reserved
0x0
1/1
1/1
1/1
1/1
Bits 7–6
Reserved
Bits 5–4
CLKDIV[1:0]
These bits set the division ratio of the clock source to determine the SYSCLK frequency.
Bits 3–2
Reserved
Bits 1–0
CLKSRC[1:0]
These bits select the SYSCLK clock source.
When a currently stopped clock source is selected, it will automatically start oscillating or clock input.