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basic interface question

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neoandrewson

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i have a basic interface question. i have a microcontroller which does not have wr/rd/cs pins. can i still connect external ram or rom in parallel to microcontroller using i/o ports and plds such that it can boot through these memories?:confused:
 
i have a basic interface question. i have a microcontroller which does not have wr/rd/cs pins. can i still connect external ram or rom in parallel to microcontroller using i/o ports and plds such that it can boot through these memories?:confused:

hi,
Whats the MCU.
Are you saying you want to boot the system from the ext ROM.?

You could preprogram the MCU with boot section then use that to control and read the ext ROM.
 
the mcu is at91sam7L.. its a arm7 based microcontroller. i want to boot from the external rom. also there is one picture data coming from cmos camera which i want to store it in nvram. this controller doesnt have rd/wr/cs pins. i mean a lot of mcu available in market dont have these pins as in 8051. how do they interface with external roms and rams? i know i look like a noob, but i cant figure it out.
 
the mcu is at91sam7L.. its a arm7 based microcontroller. i want to boot from the external rom. also there is one picture data coming from cmos camera which i want to store it in nvram. this controller doesnt have rd/wr/cs pins. i mean a lot of mcu available in market dont have these pins as in 8051. how do they interface with external roms and rams? i know i look like a noob, but i cant figure it out.

hi,
The ROM and register RAM is now internal on PIC's.

The PIC is programmed directly with the user program using a suitable programmer.

Is this what you mean.?:)
 
the mcu is at91sam7L.. its a arm7 based microcontroller. i want to boot from the external rom. also there is one picture data coming from cmos camera which i want to store it in nvram. this controller doesnt have rd/wr/cs pins. i mean a lot of mcu available in market dont have these pins as in 8051. how do they interface with external roms and rams? i know i look like a noob, but i cant figure it out.

Choice of On-chip Flash and Extensive Peripheral Set. The AT91SAM7L series has two members, the AT91SAM7L128 and the AT91SAM7L64 with respectively 128k Bytes and 64k Bytes of Flash memory.

With this much flash, why do you want to boot from external memory?
 
hi,

thnks a lot for your responses.
beebop, i'm actually trying to store picture of size much more than 1MB. also data retention on power off is important in my project. thats the reason thought of using NVRAM. booting from NVRAM could be a very useful option.
ericgibbs, i didnt get by what you mean. could you elaborate?
btw the application of the processor is in radiation environment. a radiation tolerance of memory is required. so i thought flash is a bad choice because its prone to radiation. on the other hand NVRAMs are radiation tolerant to some extent. thats the reason, on flash failure like 'latch up' condition, i can safely boot from NVRAM without bothering which part of flash is corrupted. the controller i chose satisfies most of the conditions for my project. but interfacing memory is the only thing i could not figure out.
 
ericgibbs, i didnt get by what you mean. could you elaborate?

Which of the two posts I made are you referring too.?:)
 
ericgibbs, i meant the second post..
btw is it possible to simulate those signals using GPIO? imean cs/rd/wr.. there is a compression chip which requires these signals..
 
ericgibbs, i meant the second post..
btw is it possible to simulate those signals using GPIO? imean cs/rd/wr.. there is a compression chip which requires these signals..

hi,
Yes its possible to generate theses controls signals in software.

The MCU that you are using has a large internal Flash/non volatile memory.

The MCU memory has to be programmed by your program control codes in order to carry out the instructions within your program.
So you write a program and compile it so that you have a hex code version of the program. You then load this hex into the MCU by using a MCU programmer.

To hold the large photo files, why dont you consider SD memory cards or USB memory sticks. ?
 
hi,
The MCU memory has to be programmed by your program control codes in order to carry out the instructions within your program.
So you write a program and compile it so that you have a hex code version of the program. You then load this hex into the MCU by using a MCU programmer.
i got the picture ericgibbs

To hold the large photo files, why dont you consider SD memory cards or USB memory sticks. ?
i mentioned earlier that processor is in radiation environment. i'm not sure how much these devices are secure in this environment. but thanks for the idea i'll for sure check out.:)

Yes its possible to generate theses controls signals in software.
could you direct me to some examples or give me an idea about it? it will be of great help. thank you.:)
 
could you direct me to some examples or give me an idea about it? it will be of great help. thank you.:)

Nothing to give an example of - they are just normal output pins, your program just needs to set them high and low as required.

But it's nothing to do with running a program externally, only accessing data memory.
 
hi,
could you direct me to some examples or give me an idea about it? it will be of great help. thank you.:)

As Nigel pointed out they are fairly simple to produce.

The best way to check the signals is to look at the datasheet for the ext memory you want to control.
In the datasheet will be drawings of the timing waveforms for the 3 control signals.
Just write your code so that the 3 pins of the MCU switch as per the waveforms.

If the ext memory is 8 bits wide you will have to set the MCU 8 data pins as Read or Write to match the data direction.
 
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hi,
The best way to check the signals is to look at the datasheet for the ext memory you want to control.
In the datasheet will be drawings of the timing waveforms for the 3 control signals.
Just write your code so that the 3 pins of the MCU switch as per the waveforms.

thanks ericgibbs, nigelgoodwin i think i got the idea.

But it's nothing to do with running a program externally, only accessing data memory.

yeah thats predictable..
also i have a feeling that data access will be much slower.. :eek:
thanks for your help.. :D
 
hi,

thnks a lot for your responses.
beebop, i'm actually trying to store picture of size much more than 1MB. also data retention on power off is important in my project. thats the reason thought of using NVRAM. booting from NVRAM could be a very useful option.
ericgibbs, i didnt get by what you mean. could you elaborate?
btw the application of the processor is in radiation environment. a radiation tolerance of memory is required. so i thought flash is a bad choice because its prone to radiation. on the other hand NVRAMs are radiation tolerant to some extent. thats the reason, on flash failure like 'latch up' condition, i can safely boot from NVRAM without bothering which part of flash is corrupted. the controller i chose satisfies most of the conditions for my project. but interfacing memory is the only thing i could not figure out.

I agree with Eric about the SDcard, but know nothing about radioactive environments....

The advice you are getting:
As Nigel pointed out they are fairly simple to produce.

The best way to check the signals is to look at the datasheet for the ext memory you want to control.
In the datasheet will be drawings of the timing waveforms for the 3 control signals.
Just write your code so that the 3 pins of the MCU switch as per the waveforms.

If the ext memory is 8 bits wide you will have to set the MCU 8 data pins as Read or Write to match the data direction.

is for storing data in an external chip.

But it's nothing to do with running a program externally, only accessing data memory.

So you have a couple of issues, here -
1. You wish to boot from an external memory.
2. You wish to save a large file in non volatile memory.

Eric is giving you directions for point number 2. For point number 1, I think you will need to change your make file. You may be able to relocate the reset vector to point toward an external memory, and probably your bus is not 8, but 32 bits wide?

I'm not familiar with Atmel's StrongArm, but I know the NXP Arm7's can be configured to boot from RAM by changing the make file. They also come from the factory with a boot loader installed, and it is common to interface to more RAM. Unfortunately, I know nothing about the SAM7's. :(

could you direct me to some examples or give me an idea about it? it will be of great help. thank you.:)

Perhaps someone else had done this. You could check out

https://www.embeddedrelated.com/groups/AT91SAM/1.php

for help. You will have to send email to join.
 
hi,
thanks a lot beebop.. i'll chk out..
btw the issue i have with selection of processor is like this..
1. loads of i/o (atleast greater than 40)
2. 1 i2c
3. 1 spi
4. boot from external rom (radiation hardened)
5. feature for interfacing external ram (radiation hardened)
6. good temperature of operation (preferable -40 to +120)
7. 1 adc (no considerations)
8. rtc
9. wdtc
10. 3 -timers/counters (8/16 bit)
11. ultra low power consumption (important) at extreme temperature
12. dmac
13. 1 pwm
14. speed 4 mips min
15. interrupt sources 16 min

i guess even pic 24f is sufficient.. too bad i realized late.. :eek:
any better selection possible?
 
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hi,
thanks a lot beebop.. i'll chk out..
btw the issue i have with selection of processor is like this..
1. loads of i/o (atleast greater than 40)
2. 1 i2c
3. 1 spi
4. boot from external rom (radiation hardened)
5. feature for interfacing external ram (radiation hardened)
6. good temperature of operation (preferable -40 to +120)
7. 1 adc (no considerations)
8. rtc
9. wdtc
10. 3 -timers/counters (8/16 bit)
11. ultra low power consumption (important) at extreme temperature
12. dmac
13. 1 pwm
14. speed 4 mips min
15. interrupt sources 16 min

i guess even pic 24f is sufficient.. too bad i realized late.. :eek:
any better selection possible?

Hindsight is always 20/20 :)

er... what's dmac?

I took a look at the 24FJ256GA106 data sheet. Can do 16MIPS. Only 5 external interrupts, but I think you were referring to 16 in total...

They have a Master Parallel Port(16 address lines,) so like the 8 bit PICs with the same feature, probably have a microprocessor mode.. so boot from external memory should work...

They also have a ton of peripherals - 4 x UART,5 x 16 bit timers, RTC... Nice part!

What is it that you are building? Sounds interesting!
 
hi,
er... what's dmac?
DMA controller:D
What is it that you are building? Sounds interesting!
my prof has asked few students to come up with ideas for the on board data handling systems for a pico satellite design. he has not much background of electronics. he will be choosing few best designs with the help of other faculty to decide upon his assistants for the project. i thought of competing in it. :eek: i thought of mentioning this before but many would laugh on the idea. (i've faced this before). so i had kept it low. :eek:
 
hi,

DMA controller:D

Duh! I should have thought that one through!

my prof has asked few students to come up with ideas for the on board data handling systems for a pico satellite design. he has not much background of electronics. he will be choosing few best designs with the help of other faculty to decide upon his assistants for the project. i thought of competing in it. :eek: i thought of mentioning this before but many would laugh on the idea. (i've faced this before). so i had kept it low. :eek:

Best of luck with it. I hope you win. :)
 
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