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ST7267C8 ST7267R8
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8.2 CLOCK MANAGEMENT
There are two types of run mode:
■ Low power mode: the oscillator is the clock
source (PLL is off). In this mode the USB clock
domain is switched off (no 60 MHz clock is
available).
■ Full power mode for full operation with USB. The
clock source is the PLL output (60 MHz).
After reset the device starts running in low power
mode. To switch to full power mode set MODE bit
of CCMR.
Control bits are also provided to enable or disable
the clock to individual on-chip peripherals.
In additional the application software can put the
Device in Wait, HALT.
8.2.1 Register Description
CLOCK CONTROL MODE REGISTER (CCMR)
Read/Write
Reset Value: 0000 0000 (00h)
Bit 7 = REGOFF Regulator mode in halt
0: Regulator ON
1: Regulator OFF
Put the 3.3V to 1.8V regulator in power-down
mode when the Halt instruction is executed. In this
mode the 1.8V is provided but with low current sink
capability (to maintain the RAM content and ena-
ble the wake-up). This bit has to be set before en-
tering in halt mode.
Note 1: This bit is automatically cleared after the
wake-up from halt mode.
Bit 6:3 = Reserved, must be kept cleared.
Bit 2 = LOCK PLL lock (Read Only)
This bit gives the PLL lock status.
0: PLL is not locked
1: PLL is locked
Bit 1 = MODE Run mode
This bit defines the device run mode.
0: Low power mode
1: Full power mode
Bit 0 = FRQ CPU clock frequency
This bit defines the CPU clock frequency.
0: Clock source frequency divided by 2.
1: Clock source frequency divided by 4.
Table 19. Clock frequency selection
Notes:
1. state 2 and 3 are intermediate states waiting for PLL lock
2. state 4 cannot be used with the emulator.
70
RE-
GOFF
(1)
0
000
LOCK
MOD
E
FRQ
State
(1,2)
LOCK
MODE
FRQ
CPU clk
MSCI core clk
MSCI periph clk
USB clk
0
6 MHz
12 MHz
No clk
1
0
1
3 MHz
6 MHz
12 MHz
No clk
2
0
1
0
6 MHz
12 MHz
No clk
3
0
1
3 MHz
6 MHz
12 MHz
No clk
4
1
0
30 MHz
60 MHz
5
1
15 MHz
30 MHz
60 MHz