PCMCIA interface

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Hi everybody,

A part of a project I'm designing is a PCMCIA bus card with a  32 bit
data system bus.
The system included in the card has a multicore DSP, an ARM processor,
some NOR FLASH, SDRAM memory and a FPGA.
The FPGA is used for the PCMCIA interface to the system bus and some
high speed math as a companion for DSP. The purpose of the whole PCMCIA
interface is to transfer some data from the SDRAM into PC, in real time
at 33Mhz clock rate. The card data system bus is running at 133MHz.

How you'll chose the design for the best card bus interface, knowing
there are some fast processes on the internal bus:

a. using the FPGA as a slave memory selected by the DSP and
implementing a FIFO inside the FPGA . An interrupt request will notice
the PC to start download data and empty the FIFO.
b. using DMA control over the system bus from the FPGA (FPGA as master,
DSP as slave)
c. other (please detail)

thank you,

Re: PCMCIA interface
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There's a number of things you haven't mentioned (the actual data
bandwidth?) although you say you need to transfer data at 33MHz - is
that a continuous throughput rate?

What else is connected to this memory bus? Many interfaces use the same
bus lines as the main memory system. What controller is being used? How
many clocks (minimum) per bus transaction?

All these impact the choice of interface.

The simplest is a simple memory device; much more complex is DMA access
to a dual ported RAM. Which of those (or something in between) needs
some numbers.

Specific numbers:

Throughput from FPGA (over time)
Is the burst rate from the FPGA critical? (If so, it impacts the interface)
Devices connected to the interface bus
Bus type (specifies the bus cycle information)

That would be a good start :)



Re: PCMCIA interface
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When transferring data from the FPGA to or from PC system memory,
implementing bus mastering within the FPGA will provide much higher data
bandwidth. You don't want to use a slave interface for that purpose.

Re: PCMCIA interface
Even if you implement Cardbus (essentially PCI) rather than
PCMCIA(essentially ISA) you won't get continuous 33MHz transfer other
than short periods of time. ExpressCard format can go this fast
providing the architecture behind it can support that data rate.

John Adair
Enterpoint Ltd. - Home of Tarfesock1. The Cardbus FPGA Development

vasile wrote:
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Re: PCMCIA interface

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Hi John,
I didn't heard about this standard before. It's compatible with most
PCMCIA interfaces
available on laptops ? There is somewhere a documentation available ?


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Re: PCMCIA interface

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It's unrelated to PCMCIA and is completely incompatible, having a
different connector. A few recent laptops support it, and it will
probably (eventually) replace PCMCIA. In the meantime we have the joy
of "legacy-free"!

Re: PCMCIA interface
Cardbus is a forward progression path from PCMCIA. Have a look at
www.pcmcia.org for the specifications. They do cost unfortunately. The
connector for PCMCIA/Cardbus has features to identify which sort of
card is plugged in and that is in the spec. There are host controllers
from companies like TI if you want some other sources of info. I think
Mindshare might have a book too that is worth having.

Most laptops made in the last few years, with a "PCMCIA", support the
Cardbus extension of the standard.

Expresscard is mechanically incompatible and is basically a replacement
for PCMCIA/Cardbus and is the laptop equivalent of PCI-E. It is very
rapidly replacing PCMCIA/Cardbus in new laptops.

John Adair
Enterpoint Ltd.

vasile wrote:
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Re: PCMCIA interface
Just one small clarification:

Expresscard is not "equivalent" to PCIe: the connector actually provides
both PCIe x1 and USB 2.0 ports, allowing each Expresscard slot to house
either PCIe or USB based devices... or possibly both at once, should
someone find a need for that.

Since PCIe and USB are hotplug busses, they do not need the host
controller glue logic Cardbus and PCMCIA required to bridge the void
between hotplug cards and non-hotplug consumer PCI.

John Adair wrote:
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