Basically I want to provide delay of 15 clock cycles for writing and reading through axi4 bus .Is it possible?
hankyou sir .
I have a few doubts
Firstly,the write circuit you sent to me..will be applicable for delaying each dataword in a write transaction(same situation as read).
Also I am not able to understand the cpncepr of arready.
from what I have understood
assign masked_ARREADY = ~ADDR_DONE & ARREADY; // this make outstanding 1
This masked_arready will be used by used to mask arready or just in the always block you have described in your code?
I am not able to understand this statement. further I have understood the working.
regards
Preet Kaur Walia
Hello Preet Kaur Walia,
No, it were not. The write logics insert 15 cycle delay one time.However, my new logics which were shown by HDL in the read case will be applicable to the write channel. I think by replacing 'R' for 'W', it will be OK.
This masked_arready will be used by used to mask arready or just in the always block you have described in your code? I am not able to understand this statement.
The aim of the code is to limit the number of read outstandings to one.If the master would issue more than one read addresses before responding the first data, the basic assumption of my logics would be destroyed.
Best regards,Yasuhiko Koumoto.
Sir
As you can see from the diagram I have taken from the manual of AMBAaxi it states that overlapping read bursts can occur(second address can be sent) without the first data being read back. I have thought of an alternative to this option:
shall i stop the handshaking
axhandshake=arvalid & arready;
instaed
axhandshake=arvalid & mask_arready;
I shall mask arready such that handshaking is not possible.
Also by making outstanding one you mean that the master cannot send second address before first data from first read transaction is read back?
Regards
Yes, you shall.
Also by making outstanding one you mean that the master cannot send second address before first data from first
read transaction is read back?
Yes, it does.
I am working on the read and write as per your suggestions.
The read is working fine but write is not.
As you mentioned the write will work similarly but it does not.
If I do a single write it is getting written on memory without delay(I am assuming the first data mask is not working for it)
Burst is not working.
in the write case, you should swap the meaning of data READY and VALID.That is, RREADY to WVALID and RVALID to WREADY conversions will be needed.
always@(posedge CLK) begin if(~ARESETN) WADDR_DONE <= 0; else if(AWVALID&masked_AWREADY) WADDR_DONE <= 1; else if(BVALID&BREADY) WADDR_DONE <= 0; end always@(posedge CLK) begin if(~ARESETN) FIRST_WDATA_MASK <= 0; else if(AWVALID&masked_AWREADY) FIRST_WDATA_MASK <= 1; else if(WADDR_DONE&WVALID&WREADY) FIRST_WDATA_MASK <= 0; end always@(posedge CLK) begin if(~ARESETN) wcounter <= 4'h0; else if(WADDR_DONE&masked_WVALID&masked_WREADY) wcounter <= 4'hf; else if(wcounter!=4'h0) wcoubter <= wcounter -1 ; end assign mask_pre = (wcouner != 4'h0); assign WREADY_mask = FIRST_WDATA_MASK | mask_pre; // CHANGE! assign WVALID_mask = mask_pre; // CHANGE! assign masked_WVALID = WVALID & ~WVALID_mask; // RVALID for master assign masked_WREADY = WREADY & ~WREADY_mask; // RREADY for slave assign masked_AWREADY = ~WADDR_DONE & AWREADY; // this make outstanding 1
Best regards,
Yasuhiko Koumoto.
The write is still not working.
i have a doubt. According to the timing you have assumed it states that during a write transaction the wvalid will be asserted after awready.
But in the manual ambaaxi it has been quoted that "
It is important that during a write transaction, a master must not wait for AWREADY
to be asserted before driving WVALID. This could cause a deadlock condition if the
slave is conversely waiting for WVALID before asserting AWREADY.
"
Then the logic would fade.
Hello Preet Kaur Walia.
I am sorry. I forget the current First_WDATA_Mask would be too late to stop the first data cycle.
I think that if the reset value of First_WDATA_Mask was '1' and it would become '1' at every writing done (BVALID&BREADY), it might go well.
always@(posedge CLK) begin if(~ARESETN) FIRST_WDATA_MASK <= 1; else if(BREADY&BVALID) FIRST_WDATA_MASK <= 1; else if(WADDR_DONE&WVALID&WREADY) FIRST_WDATA_MASK <= 0; end
I have done the following change to the code and it seems to work.
As we donot know that awready will be high before or after wvalid. Therefore there is possibility that first data mask will remain 1 as this condirion may not get true
the changed code
I doubt your suspicion (or maybe experiment result?) "if(WADDR_DONE&WVALID&WREADY)" might not become true because WVALID and WREADY should independent according to "A3.3.1 Dependencies between channel handshake signals" of AXI specs.
Actually, there would be some wrong scenarios with your implementation of "else if(WADDR_DONE & WREADY)" and the reset value was '0'.
If First_WDATA_Mask reset value was '0', it cannot handle the following scenario.
I think almost all case would be the <2> timing.
And "else if(WADDR_DONE & WREADY)" would not handle the following scenario.
This would be the same situation with "else if(WADDR_DONE & WVALID)".
So, I would like to propose the following description.
always@(posedge CLK) begin if(~ARESETN) FIRST_WDATA_MASK <= 1; // new change else if(AWVALID & masked_AWREADY) FIRST_WDATA_MASK <= 1; else if(WADDR_DONE & WREADY & WVALID) // should not change FIRST_WDATA_MASK <= 0; end
How about this?
Otherwize.
always@(posedge CLK) begin if(~ARESETN) FIRST_WDATA_MASK <= 1; // new change else if(AWVALID & masked_AWREADY) FIRST_WDATA_MASK <= 1; else if(WADDR_DONE & (wcount==4'hf)) // new change FIRST_WDATA_MASK <= 0; end
None of the solutions seem to work and I am not able to figure out the reason.
it's sad news.By the way, you said that if the following logic was used, it went well.
always@(posedge CLK) begin if(~ARESETN) FIRST_WDATA_MASK <= 0; else if(AWVALID & masked_AWREADY) FIRST_WDATA_MASK <= 1; else if(WADDR_DONE & WREADY) //change FIRST_WDATA_MASK <= 0; end
If it is correct, I guess that your master would not assert WVALID until getting WREADY from the slave. But it would violate the AXI specs.Can you confirm it?If you can confirm it, I should compromise the description above.To the contrary, if your slave would not assert WREADY until getting WVALID from the master, "else if(WADDR_DONE & WREADY)" would be replaced for "else if(WADDR_DONE & WVALID)".
By the way, I have found something was wrong."else if(AWVALID&masked_AWREADY)" would be strange (also in the read case).I'm sorry but I think masked_AWREADY should be AWREADY.
I am afraind WADDR_DONE would not become "1" with the previous description.Therefore, the logics would be the following.
always@(posedge CLK) begin if(~ARESETN) WADDR_DONE <= 0; else if(AWVALID&AWREADY) WADDR_DONE <= 1; else if(BVALID&BREADY) WADDR_DONE <= 0; end always@(posedge CLK) begin if(~ARESETN) FIRST_WDATA_MASK <= 1; else if(AWVALID&AWREADY) FIRST_WDATA_MASK <= 1; else if(WADDR_DONE&(wcounter==4'hf)) FIRST_WDATA_MASK <= 0; end always@(posedge CLK) begin if(~ARESETN) wcounter <= 4'h0; else if(WADDR_DONE&masked_WVALID&masked_WREADY) wcounter <= 4'hf; else if(wcounter!=4'h0) wcoubter <= wcounter -1 ; end assign mask_pre = (wcouner != 4'h0); assign WREADY_mask = FIRST_WDATA_MASK | mask_pre; // CHANGE! assign WVALID_mask = mask_pre; // CHANGE! assign masked_WVALID = WVALID & ~WVALID_mask; // RVALID for master assign masked_WREADY = WREADY & ~WREADY_mask; // RREADY for slave assign masked_AWREADY = ~WADDR_DONE & AWREADY; // this make outstanding 1
How about them?I'm sorry for you inconvenience.
The condition
always@(posedge CLK) begin
if(~ARESETN)
FIRST_WDATA_MASK <= 1; // new change
else if(AWVALID & masked_AWREADY)
FIRST_WDATA_MASK <= 1;
else if(WADDR_DONE & WREADY)
FIRST_WDATA_MASK <= 0;
end
should work fine considering that wvalid and wready need not be high together. Therefore, it might be possible that wvalid has gone high for a clock cycle and aftersometime wready goes high. Data mask should go low after that. Therefore it would not deviate from the AXI specification.
Hello,
if the releasing the FIRST_WDATA_MASK only by WREADY made your system working fine, it's a good news.I think the characteristic of "wvalid has gone high for a clock cycle and aftersometime wready goes high" would be strange because the assertions (i.e. go to High) WVALID and WREADY should be independent.If the master makes WVALID high before the slave makes WREADY high, the FIRST_WDATA_MASK logic cannot stop the data cycle.The logic will only go well if the WVAID of the master will go high after the slave would make WREADY high.Anyway, there would be the timing WVALID and WREADY will be High at the same and I wonder why "WADDR_DONE & WVALID & WREADY" would be wrong for de-asserting FIRST_WDATA_MASK.The only possibility would be WADDR_DONE was '0' at the timing when "WVALID & WREADY" was '1'. These are the cases <1> and <2> of my previous post.I will propose the new condition for releasing FIRST_WDATA_MASK.Could you please try it?
always@(posedge CLK) begin if(~ARESETN) FIRST_WDATA_MASK <= 1; // new change else if(AWVALID & AWREADY) FIRST_WDATA_MASK <= ~(WVALID & WREADY); else if(WADDR_DONE & WVALID & WREADY) FIRST_WDATA_MASK <= 0; end
Best regards,Yauhiko Koumoto.
I am working on it. Also I had a query that in the write case ,
According to me the following scenario should be followed:
We should mask wvalid as we need to stop the wvalid from the CPU from going to the slave otherwise, it will do the write transaction as and when wvalid is high.Slave will then send wready (telling the CPU it is ready to accept more data).
Whereas we are working on the contrary. As it can be seen from the first data mask situation, wready is being masked and wvalid is being sent to the slave. Therefore, there is a possibilty that slave has already written the data to memory before we are providing the delay. (in the first data mask situation we are only masking the wready)