Đang chuẩn bị liên kết để tải về tài liệu:
User Defined Primitives part 1

[ Team LiB ] 12.1 UDP basics In this section, we describe parts of a UDP definition and rules for UDPs. 12.1.1 Parts of UDP Definition Figure 12-1 shows the distinct parts of a basic UDP definition in pseudo syntax form. For details, see the formal syntax definition described in Appendix | Team LiB 12.1 UDP basics In this section we describe parts of a UDP definition and rules for UDPs. 12.1.1 Parts of UDP Definition Figure 12-1 shows the distinct parts of a basic UDP definition in pseudo syntax form. For details see the formal syntax definition described in Appendix Formal Syntax Definition. Figure 12-1 Parts of UDP Definition UDP name and terminal list primitive udp_name output_terminal_name only one allowed input_terminal_names Terminal declarations output output_terminal_name input input_terminal_names reg output_terminal_name optional only for sequential UDP UDP initialization optional only for sequential UDP initial output_terminal_name value UDP state table table table entries endtable End of UDP definition endprimitive A UDP definition starts with the keyword primitive. The primitive name output terminal and input terminals are specified. Terminals are declared as output or input in the terminal declarations section. For a sequential UDP the output terminal is declared as a reg. For sequential UDPs there is an optional initial statement that initializes the output terminal of the UDP. The UDP state table is most important part of the UDP. It begins with the keyword table and ends with the keyword endtable. The table defines how the output will be computed from the inputs and current state. The table is modeled as a lookup table. and the table entries resemble entries in a logic truth table. Primitive definition is completed with the keyword endprimitive. 12.1.2 UDP Rules UDP definitions follow certain rules 1. UDPs can take only scalar input terminals 1 bit . Multiple input terminals are permitted. 2. UDPs can have only one scalar output terminal 1 bit . The output terminal must always appear first in the terminal list. Multiple output terminals are not allowed. 3. In the declarations section the output terminal is declared with the keyword output. Since sequential UDPs store state the output terminal must also be declared as a reg. 4. The .