ARM CORTEX with multiplexed external bus interface supported by freeRTOS

jorgeq wrote on Tuesday, January 14, 2014:

Good afternoon

So far we are using 8051MX

from Philips with a proprietary RTOS for our products.

We are considering changing to FreeRTOS + expansions(TCP-IP, USB

Connectivity) and to ARM Cortex Mx to replace our existing CPU.

However we have a major draw-back we have a lot of I/O boards using

multiplexed Intel bus.

Can you advise what MCUs that support multiplexed external bus to interface with our expansion boards that

are supported by Free RTOS.

Thanks in advance

Jorge Quintela

Product development manager

davedoors wrote on Tuesday, January 14, 2014:

What do you mean by a multiplexed bus? If you mean the io and memory addresses are separate, then I dont know any modern mcus that have that.

jdurand wrote on Tuesday, January 14, 2014:

The 805x series of processors uses the same pins for address and data. The address is put out while ALE (Address Latch Enable) is high, then the bus switches to data I/O when ALE falls.

I have no idea how this bothers FreeRTOS, the OS shouldn’t know it’s going on.

Something I had run into in the past is paged memory. THAT is a pain to implement in an OS.

jorgeq wrote on Tuesday, February 04, 2014:

Thanks for your answer

In fact this should be transparent to the OS since it is solved at hardware level. I found TMPM361F10FG from Toshiba or EFM32 from Silicon LABs that support this but I could not find if these MCUs are suppported by RTOS. By support I mean kernel itself library etc. for MCU with hardware support for these peripherals.

Jorge

davedoors wrote on Tuesday, February 04, 2014:

FreeRTOS runs on any Cortex M3, Cortex M4, Cortex M4F Cortex M0 and Cortex M0+ chip.

jorgeq wrote on Tuesday, February 04, 2014:

Thanks for your answer
The processors uses the same pins for address and data. The address is put out while ALE (Address Latch Enable) is high, and latched esternally then the bus switches to adicional adresses and data when ALE falls.

EFM32 and some toshiba MCUs for example have hardware support for this. My question is are these types (or other with similar external bus capability) be supported by FreeRTOS.

JOrge