Re: Accessing (memory in) multiple types of contactless tags?

Hey thanks, good input. I will look up the specifications you mention.

So in summary I understand the following:

1. There is a standard for at least some part of the memory, for tags
that comply
2. I should have the firmware first check for the type of tag by
querying that location
3. And based on the type of tag (and its unique memory map), branch off
in to a different logic for each type of tag

Is that a fair assessment?

Thanks


Ali wrote:
ElderUberGeek wrote:
I am planning to use some type of contactless tag with an RFID reader
using one of the standard ISO protocols. I had thought, that a
ISO14443B compliant reader can read a tag complying to that standard,
regardless of the manufacturer. But I have a doubt. The memory
structures in different types of tags are different (due to different
manufacturer, size, or whatever). So how can a reader, that is supposed
to be generic, read any type of tag if it's memory structure is not
known? Or must you standardize on the type of tag you are going to use?

What I mean is, suppose I have reader R and tag T. You deploy like a
zillion of these in the field. Then you want to use another tag (T2).
Do you have to go and update the firmware in all the readers to read
the new tag's memory structure? Does not sound logical, or am I missing
something?

Thanks

EUG


Snip:

But I have a doubt. The memory structures in different types of tags are different (due >
to different manufacturer, size, or whatever).

I don't think so! I was involved for ISO 18000-6 and EPC gen2
reader, we were testing our product with different tags (different
manufactures) and yes there was a bit performance issue involved but
they were still the same for mandatory part. AFAIK, tags complying to
certain standard shall have common mandatory memory structure.
However, there is always optional part in ISO standards from memory to
command set.

Then you want to use another tag (T2). Do you have to go and update the firmware in >all the readers to read the new tag's memory structure?

Read/Write operations would return success or error depending on the
conditions. Firmware should consist on tow parts; read/write mandatory
memory and another for optional. Mandatory part will be addressing the
whole memory that will be always predefined according to underlying
standard and optional part can perform following steps to read/write
unknown memory size:

0) Though it is optional but some limit should be set (one should not
expect one GB on passive tag;-)).
1) Start from end of the mandatory memory to one block plus, IIRC IOS
18000-6 block size is 4 bytes.
2) Check the tag response and 2 possibilities can occur
a) Error : Retry to for an arbitrary number before announcing the end
of memory.
b) Success: Increment the counter to address the next block.


ali

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