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chiguoquan
Joined: 30 Mar 2006
Posts: 26
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 05 Sep 2007 4:16 A question about APB |
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The AMBA specification said that the apb bridge generates one PSELx signal for each slave,and all the slaves share the same PENABLE signal.
But the apb monitor in QuesteSim has the folowing assertion:
APB_05: The PENABLE signal should not be high when PSELx is low.
How can this assertion being satisfied while all the salves are driven by the same PENABLE signal?
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cherjier
Joined: 06 Dec 2006
Posts: 62
Helped: 4
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| 05 Sep 2007 8:13 Re: A question about APB |
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it doesn't metter the PENABLE will high or not if the PSEL is low. the PENABLE is just a globle enable signal for APB. if u are design a slave. the PSEL should decode from an address decoder to select which APB slave.
so if the APB slave device is not selected than just ignore the PENABLE, that's it..
example:
assign select = PWRITE? (PSEL & PENABLE) : (PSEL | PENABLE);
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chiguoquan
Joined: 30 Mar 2006
Posts: 26
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| 05 Sep 2007 9:37 Re: A question about APB |
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I understand what you said. I am just confused when I encounter this message:
OVL_ERROR : ASSERT_NEVER : QVL_APB_VIOLATION : The PENABLE signal should not be high when PSELx is low : Test expression is not FALSE : severity 1 : time 340 ns : clk80mdomain_tb.u6.u4.mon0.APB_05.ovl_error_t
The APB Monitor's documentation said that the APB monitor should be placed inside the slave or inside the APB bridge. Maybe the documentation make a mistake,and I should place the monitor inside the bridge,not inside the slave.
Thank you for your reply.
| cherjier wrote: |
it doesn't metter the PENABLE will high or not if the PSEL is low. the PENABLE is just a globle enable signal for APB. if u are design a slave. the PSEL should decode from an address decoder to select which APB slave.
so if the APB slave device is not selected than just ignore the PENABLE, that's it..
example:
assign select = PWRITE? (PSEL & PENABLE) : (PSEL | PENABLE); |
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