Whether LPC1768 supports bit banding for SRAM and peripherals ?

[bagyavinothap]

Hello, I am using LPC1768. My question is whether the bit band alias regions for SRAM and peripheral populated in this device or in other words whether bit banding support is available? 

I mean the following regions.

SRAM : 0x22000000 - 0x23FFFFFF

Peripheral : 0x42000000 - 0x44FFFFFF

Thanks & Regards,

Vinoth

[ianbenton]

I have a similar question about the LPC15xx

The Cortex-M3 reference manual says:

"The processor memory map includes two bit-band regions. These occupy the lowest 1MB of the SRAM and Peripheral memory regions respectively. These bit-band regions map each word in an alias region of memory to a bit in a bit-band region of memory."

and it defines the lower region of RAM as starting at 0x20000000, but in the LPC15xx that is not where the RAM is.

Does that mean that the LPC15xx cannot do bit banding as its RAM appears to be in the wrong place, in the place that ARM defines as code memory?

[jeremyzhou]

Hi  bagyavinoth ap,

Thank you for your interest in NXP Semiconductor products and 

the opportunity to serve you.

1)My question is whether the bit band alias regions for SRAM and peripheral populated in this device or in other words whether bit banding support is available? 

-- Yes, it does.

Have a great day,

TIC

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[bagyavinothap]

Thanks a lot for your input.

As per cortex M-3 specification

SRAM bit band region range : 0x20000000 - 0x200FFFFF

SRAM bit band alias region range : 0x22000000 - 0x23FFFFFF  

In LPC1768, we have following SRAM regions,

32 kB SRAM: 0x10000000 to 0x10007FFF 
16 kB SRAM0: 0x2007C000 to 0x2007FFFF
16 kB SRAM1: 0x20080000 to 0x20083FFF

So, if i understand correctly,

32kB block is not part of the bit band region and it will not support bit banding.

The 16kB blocks are part of the bit band region and it should support bit banding.

Am i right about that ?

And also as per cortex M3 specification

Peripheral bit band region range : 0x40000000 - 0x400FFFFF

Peripheral bit band alias region range : 0x42000000 - 0x44FFFFFF

In LPC1768, we have following peripheral regions,

APB0:    0x40000000 to 0x4007FFFF (32 Peripherals. Each 16 kB)
APB1:    0x40080000 to 0x400FFFFF (32 Peripherals. Each 16 kB)
AHB:    0x50000000 to 0x501FFFFF (128 Peripherals. Each 16 kB)

So if i understand correctly,

The APB peripherals will support bit banding.

AHB peripherals won't support bit banding.

Am i right about that ?

Thanks in advance.

Regards,

Vinoth

[jeremyzhou]

Hi Vinoth,

Thanks for your reply.

Both of answers are Yes, and you can learn the more detailed information in the section 34.3.2.5 Bit-banding in the UM10360.

Hope it helps.

Have a great day,

TIC

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