C8051F040-TB Silicon Laboratories Inc, C8051F040-TB Datasheet - Page 248

• Manufacturer Part Number: C8051F040-TB
• Description: BOARD PROTOTYPING W/C8051F040
• Manufacturer: Silicon Laboratories Inc
• Type: MCUr

Specifications of C8051F040-TB

• Contents: Board
• Processor To Be Evaluated: C8051F04x
• Interface Type: USB
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: C8051F040
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

C8051F040/1/2/3/4/5/6/7
19.4.2. Clock Rate Register
248
Bits7-0:
R/W
Bit7
SMB0CR.[7:0]: SMBus0 Clock Rate Preset
The SMB0CR Clock Rate register controls the frequency of the serial clock SCL in master
mode. The 8-bit word stored in the SMB0CR Register preloads a dedicated 8-bit timer. The
timer counts up, and when it rolls over to 0x00, the SCL logic state toggles.
The SMB0CR setting should be bounded by the following equation, where SMB0CR is the
unsigned 8-bit value in register SMB0CR, and SYSCLK is the system clock frequency in Hz:
The resulting SCL signal high and low times are given by the following equations:
Using the same value of SMB0CR from above, the Bus Free Timeout period is given in the
following equation:
R/W
Bit6
SFR Definition 19.2. SMB0CR: SMBus0 Clock Rate
SMB0CR
T
R/W
Bit5
T
HIGH
BFT
T

LOW




10
288 0.85

258 SMB0CR
=
R/W
Bit4

–


---------------------------------------------------- -
256 SMB0CR
–
256 SMB0CR
–
–
Rev. 1.5

SYSCLK
R/W
Bit3
SYSCLK
 SYSCLK

 SYSCLK

 1.124 6

R/W
Bit2
+

1
+
E
625ns
R/W
Bit1

SFR Address:
SFR Page:
R/W
Bit0
0xCF
0
00000000
Reset Value