Intel 8XC196MH manual Programming the Baud Rate and Clock Source, Clksrc, BV7, BV9 BV8, BV1 BV0

8XC196MC, MD, MH USER’S MANUAL

7.4.3Programming the Baud Rate and Clock Source

The SPx_BAUD register (Figure 7-7) selects the clock input for the baud-rate generator and de- fines the baud rate for all serial I/O modes. (For mode 4 with SCLKx# configured for input, the baud-rate generator is not used.) This register acts as a control register during write operations and as a down-counter monitor during read operations.

WARNING

Writing to the SPx_BAUD register during a reception or transmission can corrupt the received or transmitted data. Before writing to SPx_BAUD, check the SPx_STATUS register to ensure that the reception or transmission is complete.

SPx_BAUD	Address:	1F84H, 1F8CH
x = 0–1 (8XC196MH)	Reset State:	0000H

The serial port baud rate x (SPx_BAUD) register selects the serial port x baud rate and clock source. The most-significant bit selects the clock source. The lower 15 bits represent BAUD_VALUE, an unsigned integer that determines the baud rate.

The maximum BAUD_VALUE is 32,767 (7FFFH). In asynchronous modes 1, 2, and 3, the minimum BAUD_VALUE is 0000H when using XTAL1 and 0001H when using BCLKx. In synchronous mode 0, the minimum BAUD_VALUE is 0001H for transmissions and 0002H for receptions. In synchronous mode 4, the minimum BAUD_VALUE is 0001H for both transmissions and receptions.

8XC196MH

15

CLKSRC	BV14	BV13	BV12
7
BV7	BV6	BV5	BV4

8

BV11	BV10	BV9	BV8
			0
BV3	BV2	BV1	BV0

Bit	Bit	Function
Number	Mnemonic
15	CLKSRC	Serial Port Clock Source
		This bit determines whether the serial port is clocked from an internal or an
		external source.
		0 = signal on the BCLKx pin (external source)
		1 = input frequency on the XTAL1 pin (internal source)

Figure 7-7. Serial Port x Baud Rate (SPx_BAUD) Register

7-12