C8051F351 Silicon Laboratories Inc, C8051F351 Datasheet - Page 130

• Manufacturer Part Number: C8051F351
• Description: IC 8051 MCU 8K FLASH 28MLP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F35xr

Specifications of C8051F351

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 50MHz
• Connectivity: SMBus (2-Wire/I²C), SPI, UART/USART
• Peripherals: POR, PWM, Temp Sensor, WDT
• Number Of I /o: 17
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 768 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 3.6 V
• Data Converters: A/D 8x24b; D/A 2x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 28-VQFN Exposed Pad, 28-HVQFN, 28-SQFN, 28-DHVQFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -

C8051F350/1/2/3
17.3. Clock Multiplier
The Clock Multiplier generates an output clock which is 4 times the input clock frequency. The Clock Multi-
plier’s input can be selected from the external oscillator, or 1/2 the internal or external oscillators. This pro-
duces three possible outputs: Internal Oscillator x 2, External Oscillator x 2, or External Oscillator x 4. See
Section 17.4
The Clock Multiplier is configured via the CLKMUL register (Figure 17.5). The procedure for configuring
and enabling the Clock Multiplier is as follows:
Important Note: When using an external oscillator as the input to the Clock Multiplier, the external
source must be enabled and stable before the Multiplier is initialized. See
selecting an external oscillator source.
130
Bit7:
Bit6:
Bit5:
Bits4-2:
Bits1-0:
MULEN
R/W
Bit7
1. Reset the Multiplier by writing 0x00 to register CLKMUL.
2. Select the Multiplier input source via the MULSEL bits.
3. Enable the Multiplier with the MULEN bit (CLKMUL | = 0x80).
4. Delay for >5 µs.
5. Initialize the Multiplier with the MULINIT bit (CLKMUL | = 0xC0).
6. Poll for MULRDY => ‘1’.
MULEN: Clock Multiplier Enable
0: Clock Multiplier disabled.
1: Clock Multiplier enabled.
MULINIT: Clock Multiplier Initialize
This bit should be a ‘0’ when the Clock Multiplier is enabled. Once enabled, writing a ‘1’ to
this bit will initialize the Clock Multiplier. The MULRDY bit reads ‘1’ when the Clock Multiplier
is stabilized.
MULRDY: Clock Multiplier Ready
This read-only bit indicates the status of the Clock Multiplier.
0: Clock Multiplier not ready.
1: Clock Multiplier ready (locked).
Unused. Read = 000b; Write = don’t care.
MULSEL: Clock Multiplier Input Select
These bits select the clock supplied to the Clock Multiplier.
for details on system clock selection.
MULINIT MULRDY
Figure 17.5. CLKMUL: Clock Multiplier Control Register
R/W
Bit6
MULSEL
00
01
10
11
Bit5
R
R/W
Bit4
-
Selected Input Clock
External Oscillator / 2
Internal Oscillator / 2
External Oscillator
RESERVED
Rev. 0.4
R/W
Bit3
-
R/W
Bit2
-
Clock Multipler Output
External Oscillator x 4
External Oscillator x 2
R/W
Internal Oscillator x 2
Bit1
MULSEL
RESERVED
Section 17.4
SFR Address:
R/W
Bit0
for details on
0xBE
00000000
Reset Value