October 24, 1991
Jim Harwood
Following is a description of the Forth commands that execute when MCC-1 pushbuttons are pressed. In all cases, the commands must be in upper case and have arguments delimited by spaces before the command (standard Forth protocol).
These commands may be typed in for testing at an LSI-11/23 terminal. The TCS response to the commands will be exactly the same, whether the commands are issued from a terminal or from a program.
The end-of-stream prompt from the LSI-11 is –OK<cr><nl>. This sequence (without the period) occurs at the end of the transmission from the LSI-11 and will always occur, whether or not other data is transmitted. If an LSI-11 transmission consists of multiple lines, the lines are ended with <cr><nl>.
In this document, ASCII strings returned to the remote
computer from the LSI-11 are printed in typewriter style. Actual text is
in upper case; lower case italics indicates a general format of the returned
data, such as hh:mm:ss.
ASCII strings sent to the LSI-11 are printed here in BOLDFACE.
LSI-11 Response Formats:
You may need to know the exact format of the responses returned by the TCS LSI-11. In the examples in this document, the fields of the LSI-11 response are separated by more than one space for clarity. They actually are always separated by only one space. The fields are fixed format with respect to the number of characters in each field and the number of decimal places. For further information, see the author.
Thumbwheel
buttons:
The thumbwheels are designated as A, B, and C for RA functions, and D, E, and F for declination functions. A and D are RA and dec slew; B and E are offset; and C and F beamswitch.
The thumbwheels provide 6 digits of BCD plus sign. The format is as follows. The high order 16-bit word has the two most significant digits right justified. (The is the leading data word.) Bit 15 of this word has the sign bit in bit 15 (1=minus). The low order word is the trailing word and carries the four least significant BCD digits.
An example in hex of the double word thumbwheel data is the data for -15°23'44" as if it were dialed into the thumbwheels: 8015 (leading word), 2344 (trailing).
The thumbwheel formats are hh:mm:ss and dd:mm:ss for slew and sssss.s for offset and beamswitch.
tw lw n GP1
Arguments:
tw = trailing word
lw = leading word
n = a thumbwheel number corresponding to A – F
n is to be given in increasing powers of two. n is 1 for thumbwheel bank A, 2 for B, 4 for C, 8 for D, 16 for F, and 32 for E. This mimics individual bits set by the console hardware.
This sets the number used in the example above, -15°23'44", into the dec slew thumbwheel (D) location. The leading and trailing words are converted from hex to decimal. (For simplicity, all numbers transmitted to LSI-11/23 should be in decimal, unless specified otherwise.) Thumbwheel designator 8 is the dec slew thumbwheel (D).
Note that no error checking is done by the LSI-11/23 with respect to valid bit patterns for n. The lowest order on-bit in the n data word is treated as the thumbwheel bank number. Any other bits on in the first 6 bits of the word will be ignored.
Command
pushbuttons:
Pressing a command pushbutton causes the LSI-11/23 to execute a particular command. There are nine pushbuttons on the front panel of MCC-1 and three more equivalent (BNC jacks) on the back of the console. Switch closures at these jacks emulate pressing pushbuttons.
The pushbuttons are numbered 1 – 9 on the front panel and 10 – 12 for the rear jacks.
n is from 1 – 10. (Pushbutton commands for 11 and 12 are named differently, as explained below. There are no arguments nor is anything returned. Following are the pushbutton functions:
Slew command. Coordinates are in the thumbwheel switches A and D or are sent from an external computer. Pressing PB1 arms the TCS for a slew; holding down the deadman switch causes the slew to execute.
PB1 assumes the slew destination coordinates refer to an RA/dec slew. The command knows if coordinates were received previously from an external computer. If not, it uses the current thumbwheel coordinates for slew destination.
For the new TCS system, the operator would click on the PB1 icon and then hold down the deadman switch. First, of course, the TCS front end computer would have sent the coordinates through a thumbwheel emulation (unless the coordinates came from an external computer).
Identical to PB1 except the thumbwheel coordinates are assumed to be HA/dec instead of RA/dec. No coordinates are provided from an external computer for PB2.
Starts and stops a spiral or line scan.
Performs an "on-sky" type of offset of the displacement in the thumbwheel switch locations B and E. The RA offset as entered in thumbwheel B is divided by cosine(dec) before being output to the axis. Expects the offset displacement to be in units of tenth arcseconds.
The operator presses this button after guiding to a star after a slew.
Sets the entered (catalog) position for the prior slew to be the displayed position. Sets the position encoders to the values corresponding to the entered position. Sets this as the base position for all motions except those commanded by an external computer.
Used for operator interaction with the pointing utilities. When doing the collimation computation procedure, or the sky map procedure, the operator sets on a star and presses this pushbutton.
Coordinate difference offset execution. Uses displacements entered by a prior "C-DIFF" command, not the thumbwheels. Outputs the RA coordinate difference displacement directly, without division by cosine(dec).
Repeated calls to PB7 toggle the telescope position between the offset and base positions. PB7 offset and PB4 offset are independent of each other; they have their individual offset-from-base table entries.
Defines the current telescope position as the base position. Does not move the telescope. Zeros the offsets of all offset-from-base type of motions except for offsets provided by an external computer.
Returns the telescope to the base position from a guide or spiral scan position. Pressing the button again puts the telescope back where it started.
BNC jack on the back of the console. Causes a beamswitch to occur. Repeated calls toggle between the beamswitch position and the base position.
The following commands are named the way they are because Forth compiled names consist of the first three characters and the character count. Thus, PB10, PB11, and PB12 are identical names in Forth.
The following two "pushbuttons" are actually jacks on the back of the console.
Used in the line scan program "LINESCAN" to initiate an outward leg of the scan. A BNC cable from an external computer is plugged in here.
Used in "LINESCAN" to initiate the return leg of the scan. Accepts a BNC cable from an external computer.