Confirmation if it is OK to use reserved values for IFC timing registers in normal GPCM mode?

[sinasattari]

We have custom board designed based upon #QorIQ LS1021A ARM CPU. In the reference manual it lists the following reserved values for #IFC GPCM mode:

TACSE of IFC_FTIM0_CSn_GPCM =000:Reserved
TACO of IFC_FTIM1_CSn_GPCM =00000000:Reserved
TCS of IFC_FTIM0_CSn_GPCM =0000:Reserved 

but at the same time there is a note explaining (page 1590):

• For normal GPCM mode (write transaction) all the three timing parameters (that is, TEAHC, TACSE, and TCS) should not be programmed zero together.
• For normal GPCM mode (read transaction) all the three timing parameters (that is, TEAHC, TACSE, and TACO) should not be programmed zero together.

In our setup, we have:

TEAHC =0x1 , TACSE= 0x0, and TCS = 0x0 for write

TEAHC =0x1 , TACSE= 0x0, and TACO= 0x0 for read. 

The system is working correctly, however I wanted to get confirmation that it is OK to use "reserved" zero settings for TACSE and TCS and TACO as long as they are not all set to zero simultaneously.

[Pavel · Accepted solution]

Usually designers do not recommend using reserved values. It can produce unpredictable behavior. Designers usually do not tested behavior if reserved values are used.

Have a great day,
Pavel Chubakov

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[Pavel]

The LS1021a Reference Manual is correct.

For normal GPCM mode (write transaction) all the three timing parameters (that is, TEAHC, TACSE, and TCS) should not be programmed zero together.

For normal GPCM mode (read transaction) all the three timing parameters (that is, TEAHC, TACSE, and TACO) should not be programmed zero together.

See attached file. It is u-boot configuration file for the TWR-LS1021a board. Find the CONFIG_SYS_NOR_FTIM0 setting in this file.

Have a great day,
Pavel Chubakov

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[sinasattari]

Thank you Pavel for your reply.

I checked the file and actually we started from #LS1021ATWR as our reference design.

I wanted to make sure it is OK to use reserved value 0 for TEAHC, TACSE, TCS and TACO as long as they are not all zeros in grouping mentioned in the manual.

Best Regards,

Sina Sattari