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Mapping external RAM tp address 0.

sadhana
Associate II
Posted on August 14, 2003 at 07:40

Mapping external RAM tp address 0.

2 REPLIES 2
sadhana
Associate II
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
Associate II
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.