Epson S1C33L03 User Manual

Table 6.4 lists the control bits of clock generator.

Table 6.4  Control Bits of Clock Generator

D7

D6

D5

D4–3

D2

D1

D0

System clock division ratio 

selection

Prescaler On/Off control

reserved

CPU operating clock switch

High-speed (OSC3) oscillation On/Off

Low-speed (OSC1) oscillation On/Off

1 On

0 Off

1 OSC3

0 OSC1

1 On

0 Off

1 On

0 Off

0

0

1

0

1

1

1

R/W

R/W

–

R/W

R/W

R/W

Writing 1 not allowed.

1

1

0

0

1

0

1

0

CLKDT[1:0]

Division ratio

1/8

1/4

1/2

1/1

–

D7–4

D3

D2

D1

D0

–

HALT clock option

OSC3-stabilize waiting function

reserved

OSC1 external output control

–

0

1

0

0

–

R/W

R/W

–

R/W

0 when being read.

Do not write 1.

1 On

0 Off

1 Off

0 On

1 On

0 Off

–

–

Writing 10010110 (0x96) 

removes the write protection of 

the power control register 

(0x40180) and the clock option 

register (0x40190).

Writing another value set the 

write protection.

D7

D6

D5

D4

D3

D2

D1

D0

Power control register protect flag

0

0

0

0

0

0

0

0

R/W

SOSC1: Low-speed (OSC1) oscillation control (D0) / Power control register (0x40180)

Turns the low-speed (OSC1) oscillation on or off.

Write "1": OSC1 oscillation turned on

Write "0": OSC1 oscillation turned off

Read: Valid

The oscillation of the low-speed (OSC1) oscillation circuit is stopped by writing "0" to SOSC1, and started again

by writing "1".

Since a duration of maximum three seconds is required for oscillation to stabilize after the oscillation has been

restarted, at least this length of time must pass before the OSC1 clock can be used.

Writing to SOSC1 is allowed only when CLGP[7:0] is set to "0b10010110". Note also that if the CPU is operating

using the OSC1 clock, writing "0" to SOSC1 is ignored and the oscillation is not turned off.

At initial reset, SOSC1 is set to "1" (OSC1 oscillation turned on).

Note: This control bit is effective only when the low-speed (OSC1) oscillation circuit in the Peripheral

Block is used.

SOSC3: High-speed (OSC3) oscillation control (D1) / Power control register (0x40180)

Turns the high-speed (OSC3) oscillation on or off.

Write "1": OSC3 oscillation turned on

Write "0": OSC3 oscillation turned off

Read: Valid

The oscillation of the high-speed (OSC3) oscillation circuit is stopped by writing "0" to SOSC3, and started again

by writing "1".

Since a duration of maximum 10 ms (for a 3.3-V crystal resonator) is required for oscillation to stabilize after the

oscillation has been restarted, at least this length of time must pass before the OSC3 clock can be used.

Writing to SOSC3 is allowed only when CLGP[7:0] is set to "0b10010110". Note also that if the CPU is operating

using the OSC3 clock, writing "0" to SOSC3 is ignored and the oscillation is not turned off.

At initial reset, SOSC3 is set to "1" (OSC3 oscillation turned on).