C8051F504-IQ Silicon Laboratories Inc, C8051F504-IQ Datasheet - Page 203

• Manufacturer Part Number: C8051F504-IQ
• Description: IC 8051 MCU 32K FLASH 48-QFP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F50xr

Specifications of C8051F504-IQ

• Program Memory Type: FLASH
• Program Memory Size: 32KB (32K x 8)
• Package / Case: 48-QFP
• Mfg Application Notes: LIN Bootloader AppNote
• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 50MHz
• Connectivity: EBI/EMI, SMBus (2-Wire/I²C), CAN, LIN, SPI, UART/USART
• Peripherals: POR, PWM, Temp Sensor, WDT
• Number Of I /o: 40
• Ram Size: 4.25K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.25 V
• Data Converters: A/D 32x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Processor Series: C8051F5x
• Core: 8051
• Data Bus Width: 8 bit
• Data Ram Size: 4.25 KB
• Interface Type: I2C/SPI/UART
• Maximum Clock Frequency: 50 MHz
• Number Of Programmable I/os: 40
• Number Of Timers: 4
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: PK51, CA51, A51, ULINK2
• Development Tools By Supplier: C8051F500DK
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 32-ch x 12-bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 336-1527 - KIT DEV FOR C8051F50X
• Eeprom Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1518

Use the following equations to calculate the values for the variables for the baud-rate equation:
In all of these equations, the results must be rounded down to the nearest integer.
The following example shows the steps for calculating the baud rate values for a Master node running at
24 MHz and communicating at 19200 bits/sec. First, calculate the multiplier:
Next, calculate the prescaler:
Finally, calculate the divider:
These values lead to the following baud rate:
The following code programs the interface in Master mode, using the Enhanced Checksum and enables
the interface to operate at 19230 bits/sec using a 24 MHz system clock.
LIN0CF
LIN0CF
LIN0ADR
// Initialize the register (prescaler, multiplier and bit 8 of divider)
LIN0DAT
LIN0ADR
LIN0DAT
LIN0ADR
LIN0DAT
LIN0ADR
LIN0DAT
|= 0x40;
= 0x80;
= 0x0D;
= ( 0x01 << 6 ) + ( 0x00 << 1 ) + ( ( 0x138 & 0x0100 ) >> 8 );
|= 0x80;
= 0x0C;
= (unsigned char)_0x138;
= 0x0B;
= 0x08;
= 0x0C;
prescaler
divider
prescaler
divider
baud_rate
=
=
------------------------------------------------------------------------------------------------------------------------------------- -

2
=
multiplier
=
ln

prescaler
ln
---------------------------------------------------------------------- -
2
------------------------------------------------------------------------------------------------

-----------------------------------------------------------


multiplier
multiplier
1
0
=
+
+
--------------------------------------------------------------- -
2
1
1

1


24000000
24000000
=


+
+
1
20000
--------------- - 1
19200

1
19200
0
24000000
Rev. 1.2


+
=
+


SYSCLK
1
----------------------------- 1
baud_rate
// Activate the interface
// Set the node as a Master
// Point to the LIN0MUL register
// Point to the LIN0DIV register
// Initialize LIN0DIV
// Point to the LIN0SIZE register
// Initialize the checksum as Enhanced
// Point to LIN0CTRL register
// Reset any error and the interrupt
1



SYSCLK
0
multiplier


20000
–


+
baud_rate
200
1
19200
=


0.0417

312
------- - 1
ln2
–
+
1
=
1

312.5
–



19230.77

0
200
C8051F50x/F51x
baud_rate
=
1.644


312
------- - 1
ln2
1

–
1

203