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µVISION DEBUGGER: X2-Feature of Atmel Devices

Information in this article applies to:

  • C51 Version 6.20
  • µVision Version 2.20


I want to simulate the X2 feature of an Microchip (formerly Atmel) W&M device. The device I'm using is the T89C51CC01, but this feature is available in other devices like the T89C51CC02 or T89C51RD2.

In my hardware, I use the FLIP/BatchISP download utility to set the X2 mode bit. However, it seems that the simulator only uses the standard mode that uses 12 cycles. How can I activate the 6 cycle mode within the µVision simulator?


The µVision simulator behaves the same way as the real chip. The Simulator defaults to standard 12 cycle mode. To enable the X2 feature on the Atmel W&M devices, you must set bit 0 in the CKCON SFR (address 08Fh).

One way to do this is to create an initialization file for the debugger that enables the X2 feature. For example, create a debugger INI file that contains the following:

CKCON |=0x01               // Enable X2 bit in CKCON VTREG
reset                      // perform CPU reset
g, main                    // execute program til main

Then, under Options for Target - Debug - Use Simulator, disable the option Go till main () then enter the filename for the debugger INI file you created.


Last Reviewed: Friday, February 5, 2021

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