Hi Amit,

Query: F28388 MCAN Bit Timing Configuration for 1 Mbps Arbitration and 5 Mbps CAN-FD Data Rate

Device: TI TMS320F28388D
Peripheral: MCAN
MCAN clock: 40 MHz
Required nominal/arbitration bit rate: 1 Mbps
Required CAN-FD data bit rate: 5 Mbps
Required sampling point: 75%
Configuration interface: TI C2000Ware DriverLib MCAN_BitTimingParams

1. Current configuration

I am configuring CAN-FD communication between the TI controller and a CAN-FD analyzer. My current bit-timing configuration is:

// Initialize bit timings
bitTimes.nomRatePrescalar   = 0x3U;
bitTimes.nomTimeSeg1        = 0x6U;
bitTimes.nomTimeSeg2        = 0x1U;
bitTimes.nomSynchJumpWidth  = 0x1U;

bitTimes.dataRatePrescalar  = 0x0U;
bitTimes.dataTimeSeg1       = 0x4U;
bitTimes.dataTimeSeg2       = 0x1U;
bitTimes.dataSynchJumpWidth = 0x1U;

With an MCAN clock of 40 MHz, my understanding is that these values produce:

• Nominal/arbitration phase: 1 Mbps, 10 TQ, 80% sampling point.

• Data phase: 5 Mbps, 8 TQ, 75% sampling point.

Please confirm whether these calculations and the interpretation of the DriverLib field values are correct for the TMS320F28388D.

2. Required nominal-phase calculation

I would like to understand how to configure the nominal phase for 1 Mbps using 20 TQ and a 75% sampling point.

The intended calculation is:

• MCAN clock = 40 MHz

• Actual prescaler = 2

• Total TQ = 20

• TSEG1 = 14 TQ

• TSEG2 = 5 TQ

Bit rate:

40 MHz / (2 × 20) = 1 Mbps

Sampling point:

(1 + 14) / 20 × 100 = 75%

Could TI please confirm the corresponding nomRatePrescalar, nomTimeSeg1, nomTimeSeg2, and nomSynchJumpWidth DriverLib values, including whether each field uses a value-minus-one encoding?

3. Required data-phase calculation

My target data bit rate is 5 Mbps.

At a 40 MHz MCAN clock, using 20 TQ would produce only 2 Mbps with the minimum actual prescaler of 1:

40 MHz / (1 × 20) = 2 Mbps

Therefore, my understanding is that 5 Mbps requires 8 TQ when the actual prescaler is 1.

For a 75% sampling point, I propose:

• Actual prescaler = 1

• Total TQ = 8

• TSEG1 = 5 TQ

• TSEG2 = 2 TQ

• SJW = 1 TQ

Bit rate:

40 MHz / (1 × 8) = 5 Mbps

Sampling point:

(1 + 5) / 8 × 100 = 75%

Could TI confirm the correct dataRatePrescalar, dataTimeSeg1, dataTimeSeg2, and dataSynchJumpWidth DriverLib values for this configuration?

4. Main technical questions

1. Is it correct that the nominal phase can use 20 TQ at 1 Mbps, while the data phase must use 8 TQ at 5 Mbps when the MCAN clock is 40 MHz?

2. Can the F28388D MCAN independently use different TQ counts for the nominal and data phases?

3. Are the proposed TSEG1, TSEG2, prescaler and SJW values valid according to the F28388D MCAN timing-register constraints?

4. Please provide the exact DriverLib field values for a 75% sampling point in both phases, including register-value encoding.

5. Are any additional constraints or settings required for CAN-FD bit-rate switching, such as transmitter delay compensation (TDC), at a 5 Mbps data rate?

6. Which F28388D Technical Reference Manual sections or C2000Ware examples should be followed to verify these calculations?

My objective is to obtain a technically validated configuration for 1 Mbps nominal/arbitration and 5 Mbps data-phase communication between the F28388D and a CAN-FD analyzer.

Thank you.