TMS320C6655: SPI Boot Issue – ROM not validating Boot Parameter Table?

Eswar Majji

Part Number: TMS320C6655
Other Parts Discussed in Thread: TMS320C6657

Tool/software:

Hello TI Team,

I'm attempting to boot the TMS320C6657 from SPI NOR flash (Micron S70FS01GS) in direct ROM boot mode without IBL. I’m using the official TI-provided boot image:

Downloads\0435.C6657_directROM_Boot_example\C6657\SPIboot_ddr\bin\bootimage\app.dat

This image is written to NOR flash at offset 0x00000000 via a custom SPI writer (in emulator mode).

Boot Pin Configuration:

BOOTMODE Pin Field	Value	Description
BOOTMODE[2:0]	`110`	SPI boot
BOOTMODE[6:3]	`0000`	Parameter Table Index = 0
BOOTMODE[8:7]	`10`	Chip Select = CS0
BOOTMODE[9]	`1`	24-bit SPI address
BOOTMODE[10]	`0`	4-pin SPI
BOOTMODE[12–11]	`01`	SPI Mode = Mode 1
LENDIAN	`1`	Little Endian

Observed Behavior (on oscilloscope):

SPI clock: 500 kHz
CS#: Low for 8 bytes (~64 clock cycles)
MOSI: Sends 0x03 followed by 7 zeros (read command)
MISO: Returns the first 4 bytes from app.dat
This sequence repeats continuously
1. Why is the ROM not validating or recognizing the boot parameter table from the image?
2. Is the ROM expecting a magic word or any specific signature in the first 4 bytes?

This behavior is observed even when using the app.dat from TI's own 0435.C6657_directROM_Boot_example.

Any clarification on how the ROM determines the validity of the Boot Parameter Table would be greatly appreciated.

Thanks,
Eswar

3 months ago

0 Betsy Varughese 3 months ago

TI__Expert 4200 points

Hi Eswar,

Could you please confirm if the steps you followed are the same as those mentioned in the link: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1171336/faq-tms320c6657-how-to-run-the-direct-spi-boot-example-on-ti-c6657-evm-without-ibl .

Regards,

Betsy Varughese

0 Eswar Majji 3 months ago in reply to Betsy Varughese

Prodigy 40 points

Hi Betsy,

Yes, followed the same steps.

0 Shabary S Sundar 3 months ago in reply to Eswar Majji

TI__Intellectual 1820 points

Hi Eswar,

The engineer responsible is currently out of office. Please expect a one-day delay in response.

Regards,
Shabary.

0 Betsy Varughese 3 months ago in reply to Shabary S Sundar

TI__Expert 4200 points

Hi Eswar,

Can you try to dump first 16 bytes of flash at 0x000000 and Verify? Please confirm whether its showing all zeros after 0x03(SPI Read Command).

Regards,

Betsy Varughese

0 Eswar Majji 3 months ago in reply to Betsy Varughese

Prodigy 40 points

Hi Betsy,

To confirm: on power-up, I monitored the SPI bus using an oscilloscope. The ROM sends the 0x03 SPI read command to address 0x000000. In response, the flash always returns the first 4 bytes of the programmed image (e.g., 0x31 0x36 0x35 0x31) on the MISO line — not zeros. This pattern repeats continuously.

I'm not using the TI-provided NOR writer utility. Instead, I used my own custom SPI writer code to program the flash, because the few command sequences are different for my flash chip (S70FS01GSAGMFI010). However, I have verified that the image is written correctly by reading it back and comparing it byte-for-byte.

To further support this, I’ll attach a screenshot of the SPI waveform from my oscilloscope that shows sending the 0x03 read command and screen shot of spirom_le_swap.dat.

Please advise if this could be due to offset alignment, missing header, or padding format issues.

Thanks,
Eswar
/resized-image/__size/320x240/__key/communityserver-discussions-components-files/791/8306.pastedimage1749644944155v6.png