CCS/MSP430FR5994: What is the Max UART & SPI Baud Rates using only DCO?

I done UART benchmark for F2xx and F5xx, not for FR...

https://forum.43oh.com/topic/3413-msp430-uart-benchmark/

Hi Conroy,

The maximum baud rate of the UART can reach around 921000 , but there will be a high bit error rate.As shown in the figure below,

The SPI as the master mode it's rate can reach 4Mbit/s. Can you tell me how much higher speed do you need?  and what is it used to?

Best Regards

Johnson

We use USB-to-UART and USB-to-SPI to communicate with the MSP430FR5994.

Will ONLY using the internal DCO - provide a !!! 100% STABLE !!! 115200 Baud communications through UART?

Any other higher UART/SPI Baud rates - that are 100% STABLE?

Note: This is a "general" question - we do not want to "DESIGN" a specific high-speed USB-to-UART or USB-to-SPI device.

We simply want to use the Highest Baud-Rate possible - that is 100% STABLE.

Hi Conroy,

For UART, it is usually transmitted in 10 frames, 1 start bit, 8 data bits, and 1 stop bit. In this case, 1/2 bit is 5% with respect to 10 bits. 

you can refer to this table.

The final error is the accumulation of the SMCLK clock error resource from DCO and the error in the table. As long as it is less than 5%, accurate and stable can be achieved. As can be seen from the table, the higher the SMCLK frequency, the smaller the error.

By the way, What does 100% STABLE mean? no synchronization error ?  or  no data transmission errors?

Best Regards

Johnson

Conroy Hough said:

We use USB-to-UART and USB-to-SPI to communicate with the MSP430FR5994.

Will ONLY using the internal DCO - provide a !!! 100% STABLE !!! 115200 Baud communications through UART?

Any other higher UART/SPI Baud rates - that are 100% STABLE?

Note: This is a "general" question - we do not want to "DESIGN" a specific high-speed USB-to-UART or USB-to-SPI device.

We simply want to use the Highest Baud-Rate possible - that is 100% STABLE.

Better question for you is what BR can handle your USB-to-UART device. And who is sender? 115200 bps is too low. I didn't notice any problems where 2xx device(s) was sending data at 4 Mbps using 16 MHz DCO as MCLK / UART clock (and my USB / UART bridge based on MSP430F5510 with XT2 on board as clock source for MCLK / UART).

		mov.w #WDTPW + WDTHOLD, &WDTCTL

		mov.b &CALBC1_16MHZ, &BCSCTL1
		mov.b &CALDCO_16MHZ, &DCOCTL
        
		bis.b #UCSWRST, &UCA0CTL1

		bis.b #(BIT5 + BIT4), &P3SEL	; P3.4/P3.5 = TXD/RXD
		bis.b #UCSSEL_2, &UCA0CTL1	; SMCLK

		; 16000000 Hz  4000000 bps
		mov.b #004h, &UCA0BR0
		mov.b #000h, &UCA0BR1
		bis.b #(UCBRS_0 + UCBRF_0), &UCA0MCTL

		bic.b #UCSWRST, &UCA0CTL1

		mov.w #70, R14
		mov.b #32, R15
		
Loop		bit.b #UCA0TXIFG, &IFG2
		jnc Loop
		mov.b R15, &UCA0TXBUF
		
		add.b #1, R15
		cmp.b #127, R15
		jne Loop
		
		mov.b #32, R15
		sub.w #1, R14
		jnz Loop

If there is no factory calibrated values (and I guess it is similar to 5xx flash family) than DCO should by tuned / calibrated for selected MCLK and see what is relation (divider) to UART clock. For calibration can be also used external reference (as it is USB - UART generated transfer) similar to UART BSL in MSP430 devices.

Hi.

Using FTDI's

FT232R USB UART IC Datasheet Version 2.15
...
Data transfer rates from 300 baud to 3 Mbaud
(RS422, RS485, RS232) at TTL levels.
...

Using only internal clocks of MSP430FR5994.

What is the fastest baudrate that will be STABLE with FTDI's FT232R USB UART ?

(We need speed with no data corruption.)