C8051T635-GM Silicon Laboratories Inc, C8051T635-GM Datasheet - Page 131

• Manufacturer Part Number: C8051T635-GM
• Description: IC MCU 2KB 20PIN QFN
• Manufacturer: Silicon Laboratories Inc
• Series: C8051T63xr

Specifications of C8051T635-GM

• Program Memory Type: OTP
• Program Memory Size: 2KB (2K x 8)
• Package / Case: 20-QFN
• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SMBus (2-Wire/I²C), SPI, UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 17
• Ram Size: 768 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 3.6 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Processor Series: C8051T6x
• Core: 8051
• Data Bus Width: 8 bit
• Data Ram Size: 768 B
• Interface Type: I2C/SPI/UART
• Maximum Clock Frequency: 25 MHz
• Number Of Programmable I/os: 17
• Number Of Timers: 4
• Operating Supply Voltage: 1.8 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: PK51, CA51, A51, ULINK2
• Development Tools By Supplier: C8051T630DK
• Minimum Operating Temperature: - 40 C
• Package: 20QFN EP
• Device Core: 8051
• Family Name: C8051T63x
• Maximum Speed: 25 MHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 336-1464 - KIT DEV FOR C8051T630 FAMILY
• Eeprom Size: -
• Data Converters: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1463-5

The SMBCS1–0 bits select the SMBus clock source, which is used only when operating as a master or
when the Free Timeout detection is enabled. When operating as a master, overflows from the selected
source determine the absolute minimum SCL low and high times as defined in Equation 21.1. Note that the
selected clock source may be shared by other peripherals so long as the timer is left running at all times.
For example, Timer 1 overflows may generate the SMBus and UART baud rates simultaneously. Timer
configuration is covered in Section “24. Timers” on page 169.
The selected clock source should be configured to establish the minimum SCL High and Low times as per
Equation 21.1. When the interface is operating as a master (and SCL is not driven or extended by any
other devices on the bus), the typical SMBus bit rate is approximated by Equation 21.2.
Figure 21.4 shows the typical SCL generation described by Equation 21.2. Notice that T
twice as large as T
extended low by slower slave devices, or driven low by contending master devices). The bit rate when
operating as a master will never exceed the limits defined by equation Equation 21.1.
Setting the EXTHOLD bit extends the minimum setup and hold times for the SDA line. The minimum SDA
setup time defines the absolute minimum time that SDA is stable before SCL transitions from low-to-high.
The minimum SDA hold time defines the absolute minimum time that the current SDA value remains stable
Timer Source
Overflows
SCL
LOW
Equation 21.1. Minimum SCL High and Low Times
. The actual SCL output may vary due to other devices on the bus (SCL may be
T
Low
Figure 21.4. Typical SMBus SCL Generation
Table 21.1. SMBus Clock Source Selection
SMBCS1
T
Equation 21.2. Typical SMBus Bit Rate
HighMin
0
0
1
1
BitRate
SMBCS0
=
T
High
T
0
1
0
1
LowMin
=
f
--------------------------------------------- -
ClockSourceOverflow
Rev. 1.0
Timer 2 High Byte Overflow
=
Timer 2 Low Byte Overflow
SMBus Clock Source
--------------------------------------------- -
f
ClockSourceOverflow
Timer 0 Overflow
Timer 1 Overflow
3
C8051T630/1/2/3/4/5
1
SCL High Timeout
HIGH
is typically
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