The format of driver language statements is given below. The format is similar to that of the other FHDL languages.
<label>: <opcode> <operands>
The command format for the Windows version of FHDL is slightly different, in that the label field is missing.
<opcode> <operands>
Each statement contains a label field, and op-code field and an operands field. The label field begins at the first character of a statement and ends with a colon. A label may contain any combination of letters, digits, underlines and periods. The label field is separated from the op-code field by one or more spaces or tabs. If the label is omitted, the colon must also be omitted and the statement must begin with a space or a tab to signify that the label is omitted. Labels are ignored on most driver language statements. The opcode field must be separated from the operands field by one or more spaces or tabs. The operands field is optional for some statements, but the op-code is required for all statements. A statement is terminated by a carriage return or a semicolon. If a line ends in a comma, the statement is assumed to be continued on the next line.
The driver provides local variables and allows the nets of the Circuit Under Test (CUT) to be accessed directly. Variable names and net names consist of an arbitrary string of letters, digits, underlines and periods. Case is significant for variable names and net names so Abc, ABc, and abC are three different variable or net names. Case is not significant for driver-language keywords, so the keywords Driver, DRIVER, and DrIvEr are all the same.
A set of driver specifications must begin with a "driver" statement and end with an "enddriver" statement. These statements must be included with the rest of your FHDL specifications. At the present time, only one set of driver statements is allowed in any FHDL specification. Figure 2 illustrates the form of the driver specifications.
main: driver
<driver statements>
enddriver
The Windows version of FHDL does not use the driver or enddriver statements, because driver
commands are entered interactively.