How to Calculate the CAN speed?

Projects Networking, Protocols, and Devices
1

I am using CAN controller (MCP2515).In the data sheet of MCP2515 under SPI INTERFACE AC CHARACTERISTICS it is given

FCLK Clock Frequency — 10 MHz

Will the Same clock frequency apply to CAN also or is it different???
I have gone through the library file of MCP2515, where initialisation is done.There it is below

uint8_t mcp2515_init(uint8_t speed)
{
		
	
	SET(MCP2515_CS);
	SET_OUTPUT(MCP2515_CS);
	
	RESET(P_SCK);
	RESET(P_MOSI);
	RESET(P_MISO);
	
	SET_OUTPUT(P_SCK);
	SET_OUTPUT(P_MOSI);
	SET_INPUT(P_MISO);
	
	SET_INPUT(MCP2515_INT);
	SET(MCP2515_INT);
	
	// active SPI master interface
	SPCR = (1<<SPE)|(1<<MSTR) | (0<<SPR1)|(1<<SPR0);
	SPSR = 0;
	
	// reset MCP2515 by software reset.
	// After this he is in configuration mode.
	RESET(MCP2515_CS);
	spi_putc(SPI_RESET);
	SET(MCP2515_CS);
	
	// wait a little bit until the MCP2515 has restarted
	_delay_us(10);
	
	// load CNF1..3 Register
	RESET(MCP2515_CS);
	spi_putc(SPI_WRITE);
	spi_putc(CNF3);//Here the address of CNF3 is specified
	
/*	spi_putc((1<<PHSEG21));		// Bitrate 125 kbps at 16 MHz
	spi_putc((1<<BTLMODE)|(1<<PHSEG11));
	spi_putc((1<<BRP2)|(1<<BRP1)|(1<<BRP0));
*/
/*	
	spi_putc((1<<PHSEG21));		// Bitrate 250 kbps at 16 MHz
	spi_putc((1<<BTLMODE)|(1<<PHSEG11));//How come the BTLMODE and PHSEG11 which is in                 CNF2 can be used only CNF3 is declared
	spi_putc((1<<BRP1)|(1<<BRP0));
*/	
	spi_putc((1<<PHSEG21));		// Bitrate 250 kbps at 16 MHz
	spi_putc((1<<BTLMODE)|(1<<PHSEG11));
	//spi_putc(1<<BRP0);
    spi_putc(speed);

	// activate interrupts
	spi_putc((1<<RX1IE)|(1<<RX0IE));
	SET(MCP2515_CS);
	
	// test if we could read back the value => is the chip accessible?
	if (mcp2515_read_register(CNF1) != speed) {
		SET(LED2_HIGH);

		return false;
	}
	
	// deaktivate the RXnBF Pins (High Impedance State)
	mcp2515_write_register(BFPCTRL, 0);
	
	// set TXnRTS as inputs
	mcp2515_write_register(TXRTSCTRL, 0);
	
	// turn off filters => receive any message
	mcp2515_write_register(RXB0CTRL, (1<<RXM1)|(1<<RXM0));
	mcp2515_write_register(RXB1CTRL, (1<<RXM1)|(1<<RXM0));
	
	// reset device to normal mode
	mcp2515_write_register(CANCTRL, 0);
//	SET(LED2_HIGH);
	return true;
}

CNF3's address is given and PHSEG1 is used,I have no problem with this.But how BTLMODE and PHSEG11 can be used withour declaration of CNF11 address

[CAN Bus Bit Timing Calculator - Kvaser](https://www.kvaser.com/support/calculators/bit-timing-
calculator/)
In this website I was able to see the calculation of CAN bus parameters to the desired speed say 250kbps
so please can some one tell me how to set our desired speed with all these parameters
More over I have read the MCP2515 data sheet fully some concepts I understood and some I didnt get clearity