STM32H7 PCx_C pins unusable for boundary scan?

[regjoe]

Hello,

I used CubeMX for a design for H75x in LQFP176.

I was able to configure SDCKE0+SDNE0 signals of SDRAM Bank 1 to PC2_C and PC3_C.

Now I wanted to configure a SDRAM test using JTAG boundary scan but the JTAG tool manufacturer claims that these PCx_C pins cannot be used for boundary scan.

In the BSD file STM32H743_753_LQFP176.bsd these pins are declared as "linkage bit".

PC2_C      : linkage bit;
PC3_C      : linkage bit;

In the BSD file STM32H743_753_TFBGA240.bsd for the BGA package, which has both PCx and PCx_C pins, only the PCx_C analog pins are declared as "linkage bit". 

PC2        : inout   bit;
PC2_C      : linkage bit;
PC3        : inout   bit;
PC3_C      : linkage bit;

According to DS12117 Rev 9, the LQFP176 package has PC2_C and PC3_C pins only and the internal pads PC2 and PC3 are not routed to physical pins.

According to RM0433 12.3.1 the default state after reset is analog switch closed.

IMHO this pin is a GPIO pin after reset. Due to lack of HW I cannot verify this at the moment. 

Therefore, shouldn't be PCx_C in the LQFP176 BSD file also of type "inout bit" and can be used for boundary scan?

[ELABI.1]

Hello @regjoe,

You cannot use these pins for the SDRAM. However, you can use other available options such as pin PH3 or PC4 for SDNE0 instead of PC2_C, and pin PH2 or PC5 for SDCKE0 instead of PC3_C.

There is a limitation - Errata regarding the current on these pins precisely in the section 2.2.25.

Thank you.

ELABI.1

[regjoe]

Hello ELABI.1,

too bad.

Seems that CubeMx isn't aware of this limitation.

Here you can configure Pxy_C pins for Ethernet, SPI, SDRAM, etc. and in all speed options including high speed.

IMHO the high speed option requires a drive strength >> 1mA.

I wonder if there is a chance that SDRAM works despite the 1mA limitiation.

Probably with lower clock rate.

In DS12117 rev9 Table 8 Pxy_C pins have attributes ANA and TT_a but I cannot find a documentation regarding these attributes. Second, is there any information from ST avaliable regarding "boundary scan capable pins"?

Thank you

[regjoe]

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@regjoe wrote:

Seems that CubeMx isn't aware of this limitation.

---

Seems to me this is an well-known but not fixed bug in CubeMx

https://community.st.com/t5/stm32cubemx-mcus/bug-cubemx-should-warn-h7-users-against-pc2-c-pc3-c-pitfalls/td-p/708817 

[ELABI.1]

Hello @regjoe 

Yes, you are right. Unfortunately, CubeMX cannot display all such information.

Thank you.

ELABI.1

[regjoe]

Hello @ELABI.1 

for me, disabling the "High Speed" option or showing an extra column with the pin type "ANA" or "TT_a", as shown in DS12117 rev9 Table 8, whatever this type name exactly means, could have saved one or another from a board redesign. 

Thank you.