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dahonig
Joined: 05 May 2008
Posts: 2
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| Anyone used Atmel cryptomemory AT88SCxxxx chip I2C ? |
 Posted: Tue May 06, 2008 9:45 am |
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Hi, I'm trying to get a PIC 16F886 to talk to an Atmel cryptomemory (tm)
chip over an I2C bus. I can talk to a regular serial eeprom ok,
using the CCS i2c functions, but the slightly different AT88SC protocol is giving me problems. I'm currently pursuing a lower-level bit
banging port but wonder if anyone has done this before. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue May 06, 2008 1:05 pm |
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| Post a link to the datasheet for the exact part number that you're using. |
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dahonig
Joined: 05 May 2008
Posts: 2
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu May 08, 2008 1:17 am |
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| Quote: | | You have to write a read command to an even address then read out the bytes. |
In addition to that, there are two other things you must do:
| Quote: |
7.1 Start-up Sequence
When first powering up the device, 5 pulses are required on CLK-SCL for
reading of internal registers. |
This is probably easiest to do if you use the CCS i2c library in software
i2c mode. You can take over the bus, send the 5 pulses on SCL, and
then restore the SCL pin to the required state with the output_float()
function.
| Quote: | 7.4 Acknowledge Polling
Each command is ended with a stop condition. Certain commands are
required to be followed by an acknowledge polling sequence.
• Read Commands: No ACK polling required.
• Write Commands: ACK polling required except encrypted write
commands. Any command may be used.
• Set commands: No ACK polling required.
• Verify commands: ACK polling required with B2 or B6 commands only.
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This appnote has some sample command sequences, starting on page 6:
http://atmel.com/dyn/resources/prod_documents/doc5051.pdf |
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Guest
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| Cryptomemory i2c |
| Posted: Mon May 12, 2008 11:06 am |
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Thanks for the help. I ended up using a bit-banging implementation
of the I2C protocol, which was done by porting simple i2c functions
(eg void ll_Clockhigh(void)) in Atmel's ll_port.c (As you suggest)
This let me talk to the chip --both user memory and config memory.
Their authentication protocol isn't publicly documented enough to
code, but I found a FAE team at Atmel that volunteered to do
a PIC16 build of their library, and I'll be delighted with that.
Very nice when this stuff comes together --I was learning PIC
architecture, the IDE, compiler, i2c, and the atmel chips
at the same time.
I'm quite impressed how quickly the compiler & IDE get you up
and running. Also fascinated with the 'stuff more peripherals
into the component than you have pins' PIC architecture. |
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