How to use uart_expect()?

Utility Library
1

Hi, I am a newbie to use the UVVM_Lite for my verification. I met an question is how to use the uart_expect or uart_receive, I use it like this:

-- UART Internal Procedures   
        procedure uart_expect (
            constant data_exp           : in std_logic_vector;
            constant msg                : in string) is 
        begin
            uart_expect (
                data_exp        => data_exp,
                msg             => msg,
                rx              => tx_o,
                terminate_loop  => terminate_loop,
                max_receptions  => 1,
                timeout         => -1 ns,
                alert_level     => ERROR,
                config          => uart_bfm_config,
                scope           => C_SCOPE,
                msg_id_panel    => shared_msg_id_panel
            );
        end; 
...
for i in 0 to 255 loop 
        v_data_exp  := std_logic_vector(to_unsigned(i,8));
        --wait for 1 ps;
        --wait for 2*c_clkperiod;
        uart_expect(v_data_exp,"");
        wait for 1 ps;
        --wait for 2*c_clkperiod;
    end loop;

But the simulation is FAILURE and the log like this:

UVVM: =========================================================================================================================================================================
UVVM: ***  FAILURE #1  ***
UVVM:          7752 ns   TB seq.
UVVM:                    check_value() => Failed. std_logic  Was '0'. Expected '1'
UVVM:                    uart_expect(x"00") while executing uart_receive. Bus was active when trying to receive data. 
UVVM: 
UVVM: Simulator has been paused as requested after 1 FAILURE
UVVM: *** To find the root cause of this alert, step out the HDL calling stack in your simulator. ***
UVVM: *** For example, step out until you reach the call from the test sequencer. ***
UVVM: =========================================================================================================================================================================
UVVM: 
UVVM:

Could anybody give me same addvice?
thanks in advance!
jian

2

Hi,
The uart_expect() is an uart_receive() where you tell which value you expect to receive. An alert is raised if the received value does not match the expected.
Can you show the testbench setup, sequencer and more of the transcript? Does the simulation stop on the first loop iteration?

Br
Marius

3

Hi Marius,
Sorry for my reply is too late. The question has been solved after I have spent more hours to debug it. but thanks for your help.
Thanks!
jian

4

What was your issue? I am running into the same problem. Thanks!

5

Hi Kate,
It seems the reason for the FAILURE in the simulation transcript above is that the uart_expect() command was called when the UART was already active. A bit like a UART receiver starting to look for the 1 to 0 UART frame initiation in the middle of a UART frame (or possibly as little as a single delta cycle into the UART frame - where the line is already 0).
– Espen