Mapping external RAM tp address 0.

[sadhana]

Posted on August 14, 2003 at 07:40

Mapping external RAM tp address 0.

[sadhana]

Posted on August 14, 2003 at 05:02

I read the user manual for ST10 F280. But didn't understand how to map the external memory to address 0. Can anybody help me out in this regard?

Thanks in Advance.

[charles239955_st]

Posted on August 14, 2003 at 07:40

The ST10 devices always start executing code from address 0. Depending on the level of the /EA pin the internal Flash will be activated or not.

If /EA is low at reset disables the internal Flash and the ST10 fetches code at address 0 using the external bus by activating BUSCON0. BUSCON0 value is set up by hardware depending on the configuration of the Port0 at reset. The lines Port0 6 and 7 will configure the BTYP field of the BUSCON0 register: 00 for 8 bit data bus and demultiplexed addresses. Check the user manual section 19.7.1: System Start-up configuration for more details. Note: the default number of wait states will be 15 but this can be reprogrammed by software.