Variable Assembly Language - VAL Programming

VAL Programming

Several conventions apply to numerical values to be supplied to VAL commands and instructions. Preceding each monitor-command description are two symbols indicating when the command can be typed by the user. A dot (.) signifies the command can be performed when VAL is in its top-level monitor mode and no user program being executed (that is, when the system prompt is a dot). An asterisk (*) indicates the command can be performed at the same time VAL is executing the program (that is, when the system prompt is an asterisk). If both symbols are present the command can be executed in either case. Most monitor commands and program instructions can be abbreviated. When entering any monitor command or program instruction, the function name can be abbreviated to as many characters as are necessary to make the name unique.

For commands and instructions, angle brackets, < >, are used to enclose an item which describes the actual argument to appear. Thus the programmer can supply the appropriate item in that position when entering the command or instruction. Note that these brackets used here are for clarification, and are never to be included as part of a command or instruction.

Many VAL commands and instructions have optional arguments. For notations, optional arguments are enclosed in square brackets, . If there is a comma following such an argument, the comma must be retained if the argument is omitted, unless nothing follows. For example, the monitor BASE command has the form:

To specify only a 300-millimeter change in the Z direction, the command could be entered in any of the following ways:

• BASE 0,0,300,0
• BASE ,,300,
• BASE ,,300

Note that the commas preceding the number 300 must be present to correctly to relate the number with a Z-direction change. Like angle brackets, square brackets are never entered as part of a command or instruction.

Several types of numerical arguments can appear in commands and instructions. For each type there are restrictions on the values that are accepted by VAL. The following rules should be observed:

1. Distances are entered to define locations to which the robot is to move. The unit of measure for distances is millimeter, although units are never explicitly entered for any value. Values entered for distances can be positive or negative, with their magnitudes limited by a number representative of the maximum reach of the robot (for example, 1024 mm and 700 mm for the PUMA 500 and PUMA 250 robots, respectively). Within the resultant range, distance values can be specified in increments of 0.01 mm. Note, however, that some values cannot be represented internally, and are stored as the nearest representable value.
2. Angles in degrees are entered to define and modify orientations the robot is to assume at named locations, and to describe angular positions of robot joints. Angle values can be positive or negative, with their magnitudes limited by 1800 or 3600 depending on the usage. Within the range, angle values can be specified in increments of 0.01°. Values cannot be represented internally, however they are stored as

nearest representable value.