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deltatech
Joined: 22 Apr 2006
Posts: 87
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| Some very Basic Questions About External Memory |
 Posted: Sun Jun 25, 2006 10:54 am |
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Some very basic questions about memory from a fairly newbie so please respond kindly. !
1 what is the difference between EEPROM (9536) and SRAM (PCFF8570) ?
2 Where would you use either .
3 Both memory capacity is 256 , what if I need more memory ? .
I have used CCS example EX_EXTEE.C and EX_SRAM . They work fine.
4 But they only ask for a Two digit address . So I if I want to address more memory how do I adopt these examples to read more address.
5 I want to read the following table in to either external memory . can this be done . ? Ie is there enough memory to accommodate this table .
6 How do I calculate how much memory I need . ? For example for the table below how do I work out how much memory this table needs .
7 If I wanted to write the following Table in say PCFF870 how would I do that ? because CCS WRITE_EXT_SRAM( address, value );andREAD_EXT_SRAM( address )only write and read one address at a time .
8 The other thing I have noticed is If I write TT and read it back its no longer TT but FF . So how do I save alpha characters ABCDEFGH etc .
As you can I am new to memory this is the first time I have connected memory on breadboard with a PIC and I am still learning .
Many Thanks In Advance ..
| Code: | 1 12 239 539 139 639 939 439 739 839
2 12 339 639 239 739 1039 539 839 939
3 12 439 739 339 839 1139 639 939 1039
4 12 539 839 439 939 1239 739 1039 1139
5 12 639 939 539 1039 1339 839 1139 1239
6 12 739 1039 639 1139 1439 939 1239 1339
7 12 839 1139 739 1239 1539 1039 1339 1439
8 12 939 1239 839 1339 1639 1139 1439 1539
9 12 1039 1339 939 1439 1739 1239 1539 1639
10 12 1139 1439 1039 1539 1839 1339 1639 1739
11 12 1239 1539 1139 1639 1939 1439 1739 1839
12 12 1339 1639 1239 1739 2039 1539 1839 1939
13 12 1439 1739 1339 1839 2139 1639 1939 2039
14 12 1539 1839 1439 1939 2239 1739 2039 2139
15 12 1639 1939 1539 2039 2339 1839 2139 2239
16 12 1739 2039 1639 2139 039 1939 2239 2339
17 12 1839 2139 1739 2239 139 2039 2339 039
18 12 1939 2239 1839 2339 239 2139 039 139
19 12 2039 2339 1939 039 339 2239 139 239
20 12 2139 039 2039 139 439 2339 239 339
21 12 2239 139 2139 239 539 039 339 439
22 12 2339 239 2239 339 639 139 439 539
23 12 039 339 2339 439 739 239 539 639
24 12 139 439 039 539 839 339 639 739
25 12 239 539 139 639 939 439 739 839
26 12 339 639 239 739 1039 539 839 939
27 12 439 739 339 839 1139 639 939 1039
28 12 539 839 439 939 1239 739 1039 1139
29 12 639 939 539 1039 1339 839 1139 1239
30 12 739 1039 639 1139 1439 939 1239 1339
31 12 839 1139 739 1239 1539 1039 1339 1439 |
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asmallri
Joined: 12 Aug 2004
Posts: 1635
Location: Perth, Australia
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| Posted: Sun Jun 25, 2006 7:58 pm |
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It is not a good idea post in bold face it make it difficult to read. Generally bold should only be used to emphasise a specific point.
| Quote: |
1 what is the difference between EEPROM (9536) and SRAM (PCFF8570) ? |
EEPROM = Electrically Eraseable Read Only Memory. Once you wite to it, information is retained through power cycling - depending on the device it can retain the information for up to 100 years. It takes typically 5 to 20ms to write either a single byte or a page depending on the device. You could use higher capacity EEPROMs. Microchip has a 512K bit (64K byte) version 24LC512
SRAM - Static RAM. Data is lost in the event of power loss. Write access is very fast (no 5 to 20ms write delay). SRAMs are rather limited in capacity compared to EEPROM sizes. However there is an alternative. A FRAM such as the RAMTRON 24C256 is a 256K bit (32K byte) device that has the access speed of RAM but is non volatile - retains program through power cycle.
_________________
Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!! |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Mon Jun 26, 2006 1:43 am |
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You are asking a lot of questions, many of them so easy to answer that I'm wondering if you have even tried to look up the answer yourself.
| Quote: | | 1 what is the difference between EEPROM (9536) and SRAM (PCFF8570) ? |
Looking at the questions you are asking I'm wondering why you are comming up with these specific part numbers. What made you decide to use external memory? Save yourself (and us) a lot of time by buying a PIC with more internal memory. |
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