C8051F350DK Silicon Laboratories Inc, C8051F350DK Datasheet - Page 135

• Manufacturer Part Number: C8051F350DK
• Description: DEV KIT FOR F350/351/352/353
• Manufacturer: Silicon Laboratories Inc
• Type: MCUr

Specifications of C8051F350DK

• Contents: Evaluation Board, Power Supply, USB Cables, Adapter and Documentation
• Processor To Be Evaluated: C8051F35x
• Interface Type: USB
• Silicon Manufacturer: Silicon Labs
• Core Architecture: 8051
• Silicon Core Number: C8051F350
• Silicon Family Name: C8051F35x
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: C8051F350, 351, 352, 353
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1083

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. System Clock Selection’ on page 136 for details on system clock selection.
The Clock Multiplier is configured via the CLKMUL register (SFR Definition 17.4). The procedure for con-
figuring 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 Section “17.4. System
Clock Selection’ on page 136 for details on selecting an external oscillator source.
Bit7:
Bit6:
Bit5:
Bits4–2: Unused. Read = 000b; Write = don’t care.
Bits1–0: MULSEL: Clock Multiplier Input Select
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).
These bits select the clock supplied to the Clock Multiplier.
MULINIT MULRDY
R/W
Bit6
SFR Definition 17.4. CLKMUL: Clock Multiplier Control
MULSEL
00
01
10
11
Bit5
R
R/W
Bit4
—
Selected Input Clock
External Oscillator / 2
Internal Oscillator / 2
External Oscillator
RESERVED
Rev. 1.1
R/W
Bit3
—
R/W
Bit2
—
C8051F350/1/2/3
Clock Multipler Output
External Oscillator x 4
External Oscillator x 2
R/W
Internal Oscillator x 2
Bit1
MULSEL
RESERVED
SFR Address:
R/W
Bit0
0xBE
00000000
Reset Value
135