In How to create and use a sequence, we saw that a sequence calls on the tasks start_item() and finish_item(). You can avoid putting all these statements in your code by simply calling UVM sequence macros `uvm_do or `uvm_do_with. At compile time, these macros will be substituted with calls to start_item() and finish_item(). There are primarily four types of UVM macros that can be executed on the default sequencer.
Macros `uvm_do_*
You have to provide a uvm_sequence_item object or a sequence and internally, it will do the following:
- create the item if necessary using
`uvm_create. If you don't want it to create an item, use`uvm_send. - randomize the item or sequence
- call the
start_item()andfinish_item()if its auvm_sequence_itemobject - call the
start()task if its a sequence
- `uvm_do : execute this sequence on default sequencer with the item provided
- `uvm_do_with : override any default constraints with inline values.
- `uvm_do_pri : execute based on the priority value, used when running multiple sequences simultaneously.
- `uvm_do_pri_with: execute based on priority and override default constraints with inline values
`uvm_do_* macros will identify if the argument provided is a sequence or a sequence item and will call start() or start_item() accordingly.
Example
The sequence below will generate four items, randomize them and send to driver - See simulation results !
class base_sequence extends uvm_sequence #(my_data);
`uvm_object_utils (base_sequence)
...
virtual task body ();
`uvm_info ("BASE_SEQ", $sformatf ("Starting body of %s", this.get_name()), UVM_MEDIUM)
`uvm_do (req)
`uvm_do_with (req, { data == 8'h4e;
addr == 8'ha1; })
`uvm_do_pri (req, 9)
`uvm_do_pri_with (req, 3, { data == 8'hc5; })
`uvm_info ("BASE_SEQ", $sformatf ("Sequence %s is over", this.get_name()), UVM_MEDIUM)
endtask
...
endclass
The variable req is already declared and defined in the parameter for the sequence class. So, req is of the type my_data. The `uvm_do_* macros will utilize a default in-built sequencer called m_sequencer. If you want the sequence to be executed on some other user-defined sequencer, you have to call `uvm_do_on_* macros as shown below :
`uvm_do_on (SEQ_OR_ITEM, SEQR)
`uvm_do_on_pri (SEQ_OR_ITEM, SEQR, PRIORITY)
`uvm_do_on_with (SEQ_OR_ITEM, SEQR, CONSTRAINTS)
`uvm_do_on_pri_with (SEQ_OR_ITEM, SEQR, PRIORITY, CONSTRAINTS)
Structure
Note : All the macros are coded using `define within UVM, and each of them calls `uvm_do_on_pri_with with appropriate arguments. For example,
`define uvm_do (SEQ_OR_ITEM)
`uvm_do_on_pri_with (SEQ_OR_ITEM, m_sequencer, -1 {})
`define uvm_do_on_with (SEQ_OR_ITEM, SEQR, CONSTRAINTS)
`uvm_do_on_pri_with (SEQ_OR_ITEM, SEQR, -1, CONSTRAINTS)
Simulation Results
CDNS-UVM-1.1d (14.10-s013)
(C) 2007-2013 Mentor Graphics Corporation
(C) 2007-2013 Cadence Design Systems, Inc.
(C) 2006-2013 Synopsys, Inc.
(C) 2011-2013 Cypress Semiconductor Corp.
----------------------------------------------------------------
UVM_INFO @ 0: reporter [RNTST] Running test base_test...
UVM_INFO @ 0: reporter [UVMTOP] UVM testbench topology:
------------------------------------------------------------
Name Type Size Value
------------------------------------------------------------
uvm_test_top base_test - @2636
m_top_env my_env - @210
m_drv0 my_driver - @204
rsp_port uvm_analysis_port - @2840
seq_item_port uvm_seq_item_pull_port - @2789
m_seqr0 my_sequencer - @2739
rsp_export uvm_analysis_export - @2930
seq_item_export uvm_seq_item_pull_imp - @3478
arbitration_queue array 0 -
lock_queue array 0 -
num_last_reqs integral 32 'd1
num_last_rsps integral 32 'd1
m_seqr1 uvm_sequencer - @2871
rsp_export uvm_analysis_export - @3565
seq_item_export uvm_seq_item_pull_imp - @4105
arbitration_queue array 0 -
lock_queue array 0 -
num_last_reqs integral 32 'd1
num_last_rsps integral 32 'd1
------------------------------------------------------------
UVM_INFO ./tb/my_pkg.sv(96) @ 0: uvm_test_top.m_top_env.m_drv0 [my_driver] Applying initial reset
UVM_INFO ./tb/my_pkg.sv(100) @ 390000: uvm_test_top.m_top_env.m_drv0 [my_driver] DUT is now out of reset
UVM_INFO ./tb/my_pkg.sv(107) @ 390000: uvm_test_top.m_top_env.m_drv0 [my_driver] Waiting for data from sequencer
UVM_INFO ./tb/my_pkg.sv(173) @ 390000: [email protected]@seq1 [seq1] Starting body of seq1
UVM_INFO ./tb/my_pkg.sv(120) @ 410000: uvm_test_top.m_top_env.m_drv0 [DRV] Driving data item across DUT interface
req: ([email protected]) {
data: 'hfb
addr: 'h38
begin_time: 390000
depth: 'd2
parent sequence (name): seq1
parent sequence (full name): uvm_test_top.m_top_env.m_seqr1.seq1
sequencer: uvm_test_top.m_top_env.m_seqr1
}
UVM_INFO ./tb/my_pkg.sv(107) @ 410000: uvm_test_top.m_top_env.m_drv0 [my_driver] Waiting for data from sequencer
UVM_INFO ./tb/my_pkg.sv(120) @ 430000: uvm_test_top.m_top_env.m_drv0 [DRV] Driving data item across DUT interface
req: ([email protected]) {
data: 'h4e
addr: 'ha1
begin_time: 410000
depth: 'd2
parent sequence (name): seq1
parent sequence (full name): uvm_test_top.m_top_env.m_seqr1.seq1
sequencer: uvm_test_top.m_top_env.m_seqr1
}
UVM_INFO ./tb/my_pkg.sv(107) @ 430000: uvm_test_top.m_top_env.m_drv0 [my_driver] Waiting for data from sequencer
UVM_INFO ./tb/my_pkg.sv(120) @ 450000: uvm_test_top.m_top_env.m_drv0 [DRV] Driving data item across DUT interface
req: ([email protected]) {
data: 'hd8
addr: 'h2d
begin_time: 430000
depth: 'd2
parent sequence (name): seq1
parent sequence (full name): uvm_test_top.m_top_env.m_seqr1.seq1
sequencer: uvm_test_top.m_top_env.m_seqr1
}
UVM_INFO ./tb/my_pkg.sv(107) @ 450000: uvm_test_top.m_top_env.m_drv0 [my_driver] Waiting for data from sequencer
UVM_INFO ./tb/my_pkg.sv(120) @ 470000: uvm_test_top.m_top_env.m_drv0 [DRV] Driving data item across DUT interface
req: ([email protected]) {
data: 'hc5
addr: 'h8
begin_time: 450000
depth: 'd2
parent sequence (name): seq1
parent sequence (full name): uvm_test_top.m_top_env.m_seqr1.seq1
sequencer: uvm_test_top.m_top_env.m_seqr1
}
UVM_INFO ./tb/my_pkg.sv(107) @ 470000: uvm_test_top.m_top_env.m_drv0 [my_driver] Waiting for data from sequencer
UVM_INFO ./tb/my_pkg.sv(179) @ 470000: [email protected]@seq1 [seq1] Sequence seq1 is over
UVM_INFO ./tb/my_pkg.sv(126) @ 470000: uvm_test_top.m_top_env.m_drv0 [my_driver] Finished DUT simulation
--- UVM Report catcher Summary ---
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