MON51: Error 22 (No Code Memory at Address xxxxH)

Information in this article applies to:

• C51 Version 5 and Later

QUESTION

I'm using the Keil Debugger to download my program using the MON51 monitor in my target hardware. When the debugger starts downloading my program, I receive the following error message:

ERROR 22 (NO CODE MEMORY AT ADDRESS 0045H)

Why do I receive this error?

ANSWER

When the monitor downloads your program to the target hardware, it writes to XDATA and reads from CODE to confirm that each byte was written correctly.

This message indicates that the monitor wrote a value to address X:0045h, read the value back from C:0045h, and the two values were different. So, the code that was downloaded and written to XDATA memory could not be read from the corresponding CODE address. When your program gets to address 0045h, it will not execute the instruction that it should.

Usually, this error indicates that you do not have von Neumann memory at the specified address.

One solution is to use the debugger to connect to the monitor without loading a program. Then, change the XDATA memory contents and view the CODE memory to see if it changes. If it does not, then there is a problem in your hardware or you have an inaccurate memory map.

MORE INFORMATION

• If you use the EZ-USB devices, refer to section 9.10 or section 12.10 of the EZ-USB Technical Reference Manual.
• Refer to Application Note 126: Using the Cypress EZ-USB AutoVector Interrupts for more information about the Autovector on the EZ-USB chip.

Last Reviewed: Thursday, February 25, 2021