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Beginner
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Serial data writing problem

I write to 16-bit RAM.

The message I write is

CONT_WRITE ADR_MSB ADR_LSB DATA0_MSB DATA0_LSB …. DATAn_MSB DATAn_LSB

where

CONT_WRITE –command - continuous write .

ADR_MSB ADR_LSB -start address. (sspi_cont_addr <= ADR_MSB & ADR_LSB)

DATA0_MSB DATA0_LSB – a pair bytes of data.

---------------------------CONTINIOUS WRITE------------------------------------- when ST_CONT_WRITE_1 => --first address and data SITAL_1553_1_ADR <= sspi_cont_addr; SITAL_1553_1_CS <= '1'; SITAL_1553_1_WR <= '1'; SITAL_1553_1_RD <= '0'; st_count := 0; byte_idx := 0; --skip command and address if (bytes_counter = X"03") then SitalState <= ST_CONT_WRITE_2; end if; when ST_CONT_WRITE_2 => if (cs2 = '0') then if (new_byte = '1') then --next data if (byte_idx = 2) then byte_idx := 0; --next address sspi_cont_addr <= sspi_cont_addr + '1'; end if; SitalState <= ST_CONT_WRITE_3; end if; else --end of message SitalState <= ST_SITAL_IDLE; end if; when ST_CONT_WRITE_3 => --set a word from bytes case byte_idx is when 0 => sspi_cont_data(15 downto 8) <= sspi_data; SitalState <= ST_CONT_WRITE_2; when 1 => sspi_cont_data(7 downto 0) <= sspi_data; reg_count := 0; --a word is complete SITAL_1553_1_ADR <= sspi_cont_addr; SITAL_1553_1_DIN <= sspi_cont_data; SitalState <= ST_CONT_WRITE_4; when others => end case; byte_idx := byte_idx + 1; when ST_CONT_WRITE_4 => reg_count := reg_count + 1; --set the address and the data SITAL_1553_1_ADR <= sspi_cont_addr; SITAL_1553_1_DIN <= sspi_cont_data; --expose the data on the bus for x ckocks if (reg_count = 8) then SitalState <= ST_CONT_WRITE_2; end if;

I see all words in RAM. But sometimes some word is ''broken''. Say instead of 0x8000 I see 0x8100. I send 30 byte (15 words). Usually I see ''broken'' words 2 and 14, sometimes others.

What possibly can be the problem?

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3 Replies
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Employee
2 Views

Hi,

May I know how you are verifying the data , is it through signal tap

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Beginner
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It's hard to catch the problem with signal tap. But I found the problem. It was clocks synchronization problem.

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Employee
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Hi EEren,

Glad to to know that the issue is been resolved

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