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connecting tristates

Hi,

Currently I'm working on a OPB to ISA bridge to be included as a peripheral in a Microblaze system. To verify that the bridge works, I've also made a GPIO that is connected as a peripheral on the ISA bus. The ISA data bus is bidirectional and is thus implemented as a tristate port. Since the data port on the ISA GPIO also is bidirectional, that is also implemented as a tristate. The problem is that when the two tristate signals are connected in the system.mhs file (data = isa_sd) XST interprets that to connect the isa_sd_i with data_i, isa_sd_o with data_o, and isa_sd_t with data_t. I have also tried to separate the data ports on the GPIO side, but I haven't worked out how to specify that isa_sd_o should be connected to data_i and isa_sd_i to data_o.

Does anyone with more experience on this matter than me have any good suggestions on how to solve the problem?

Johan

Reply to
Johan Bernspång
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You can use SR 16636 as a starting point.

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Once you have the INOUT port broken out to the individual _T, _I, and _O ports in the MPD.

You can then assign these ports in the MHS.

BEGIN isa_gpio PORT isa_sd_o =3D data_i PORT isa_sd_i =3D data_o END

BEGIN opb_gpio PORT GPIO_I =3D data_i PORT GPIO_O =3D data_o END

Johan Bernsp=E5ng wrote:

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--=20 / 7'7 Paulo Dutra ( snipped-for-privacy@xilinx.com) \ \ ` Xilinx snipped-for-privacy@xilinx.com / / 2100 Logic Drive

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Reply to
Paulo Dutra

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