Question about using 8051 Flash Memory

[glenjoy]

8051 Flash Question

Can I load the bootloaders in the 8051 Flash Memory and still use an external data memory for emulation of the EPROM? Say example the loader in Yeralans book, instead of putting the loader to an EPROM, I will just put it in the FLASH memory and still have an external data memory.

 

[silvio]

Re: 8051 Flash Question

Hi Glenjoy,

Yes you can do.
What 8051 with flash inside, do you have in mind ?

Regards,
Silvio

 

[marie65]

Beware of mapping the external RAM to code space in order to be able to execute the code from there. OR RD signal and PSEN trough a gate

 

[glenjoy]

Re: 8051 Flash Question

Hi Glenjoy,

Yes you can do.
What 8051 with flash inside, do you have in mind ?

Regards,
Silvio

I am planning to use DS89C420, or DS5000.

 

[glenjoy]

Beware of mapping the external RAM to code space in order to be able to execute the code from there. OR RD signal and PSEN trough a gate

Btw, will I will not anymore use a NAND Gate, because it acts only as a selector betwwen the DATA and the EPROM?


The NVSRAM will also act as an EPROM.

 

[silvio]

Re: 8051 Flash Question

Hi Glenjoy,

If you plan to use 89C420 the main concern is the ROMSIZE feature.
Read more about implementing a bootstrap loader (other technique in addition to built-in ROM loader) in Dallas Application Notes 102
h**p://pdfserv.maxim-ic.com/en/an/AN577.pdf
and the software example.
h**p://www.maxim-ic.com/products/microcontrollers/software/app_note_software/hsm_load.exe

There are a number of software consideration using ROMSIZE feature to switch between on- and off-chip memory.
For particular 89C420 read more in Ultra-High-Speed Flash Microcontroller User’s Guide
h**p://www.maxim-ic.com/products/microcontrollers/pdfs/DS89c420_user_guide.pdf
in Section 6: Memory Access

Care must be taken if you plan to use the external memory, since this approach has serious constraint regarding tAA of memory at full 89C420 speed, configured for
PAGE MODE 1 EXTERNAL TIMING-PAGES 1:0 = 00b (ONE CYCLE)

For DS5000FP and/or DS5000T you may use an EPROM or FLASH for program storage, though this sacrifices
features such as the Bootstrap loader and program encryption. If you plan to do that read the design precautions when using a non-battery backed approach.
h**p://www.maxim-ic.com/appnotes.cfm/appnote_number/553/ln/en

Glenjoy wrote:

The NVSRAM will also act as an EPROM

Yes, but with additional features that you can update the code.

Glenjoy wrote:

Btw, will I will not anymore use a NAND Gate, because it acts only as a selector betwwen the DATA and the EPROM?

If you plan to use DS5000FP then you can forget about external gate since you'll use the byte-wide bus and /CE1.
But for program code stored in external Flash for 89C420 or other, you still need the gate in order to write the updated code and run then from XRAM space and read it as well.
Just because when you write the Flash, it's mapped in XRAM space, and when read the opcode you use PSEN for Flash access.
BTW is a AND gate whom output goes toward /OE of Flash memory.

Regards,
Silvio

 

[glenjoy]

Re: 8051 Flash Question

Hi,

The real main purpose of this project is for me to load codes to the NVSRAM then use the NVSRAM in romless chips, have anyone of you tried this?

 

[silvio]

Re: 8051 Flash Question

Hi Glenjoy,

I know that feeling.
Using micro with ROM bootloader for loading codes in NVSRAM then pass the memory to ROMless micro. Obvious the new NVSRAM will contain a "software" bootloader (for ROMless micro) in order to avoid pulling out the NVSRAM from the board and reprogramm again, if was a major failure due to an unexpected write to the "software bootloader" main program area.
I wrote the above things because I didn't see any better solution to start a system with ROMless micro driven by NVSRAM only (no "hardware boot" in EPROM or FlashROM) suitable to be reprogrammed easily through serial port, for example. The NVSRAM must be programmed somehow. If your choise was through another development board then the solution is as good as NVSRAM programmed by a program running in ordinary PC.

Regards,
Silvio

 

[glenjoy]

Re: 8051 Flash Question

I was just thinking of making the NVSRAM act like an EPROM in ROMLESS 8051's, so than no more messing with EPROM eraser and EPROM burner, can anyone help or ready made codes?