Lesson Three
Design and library objects
Design Object
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Verilog-level
Object divided into six: Design, Clock, Port, Net , Cell and Pin.
Few differences: Design is currently located in the top __ __, and __ Cell is instantiated in the top level module __; Port is the port that communicates with the outside of the top, and Pin is the example of the module and an external module to interact port.
** Object concept is similar to the programming language "objects." -
Schematic level
Depending on the selected viewing angle can be different types of object with the same name, for example, may be a CLK clock, net, it may be a PIN, when writing tcl statements need to distinguish between different attributes. Especially the design and cell conversion can occur at any time.
Commands
Q: How to disambiguate?
For example command set_load 5 SUM, SUM is no type specified net or port, then the capacitive load 5pF load can not be determined in what place will be loaded on the default port.
- get_ * command
set_load 5 [get_nets SUM]
get_ command returns the object may have a corresponding type and name, obejct name which you can also use the " " and "?" wildcards. If you do not meet the conditions of the object, it will return "empty collection".
- all_ command
according to the type of the corresponding position, returns all objects of the corresponding type.
remove_from_collection [all_inputs] [get_ports CLK]
This command can be one of the front bracket specified concentration thereof was removed after a set of brackets.
Command Summary:
Attributes & Collections
Each type has its own unique attributes (attributes), for example,
the ports: direction, driving_cell_rise, Load, max_capacitance, etc.
Cells:. Dont_touch, is_hierarchical, is_mapped, is_sequential, etc
the DC constraint file is essentially impose constraints on the attribute object .
NOTE: After performing get_ and all_ command, DC generates the object corresponding to the set (collection), and returns the set of corresponding handle (handle) i.e. "pointer"
set foo [get_ports p*] //foo是collection的名字
sizeof_collection $foo //f输出foo内objection的个数
query_objects $foo //输出foo内所有object的列表
filter_collection [get_cells *] "reg_name =~ AN*" //从cell中过滤出以AN开头的object
foreach_in_collection cell [get_cells -hier * -filter "is_hierarchical == true"]
//相当于对符合条件的object遍历
- Supplementary
Q: DC concept of an array do?
A: Yes, you can use the command "set ages (zhangsan) 23" may be set to age zhangsan assignment element 23.
"echo $ ages (zhangsan)" to return property values.
DC as well as an array of __env__ own pre-defined with the command "array names env" can output the names of all the elements of env in fact is a collection of environment variables in this array.
Another command getenv / get_unix_variable can get the environment variables.
