Dec-P Support For Type 154 Stepping Motor Controllers

M. Glass
1 June 1984

Dec-P supports all the options on the 154 card even though the immediate application does not demand them. This means you can create data base entries for the Setting, Basic Status, and Basic Control properties. Any Reading property you might want to create presumably reads some separate position sensor.

All three properties have identical SSDNs in the data base, to wit:

0 0
0 OID = 1E (hex)
crate slot
0 0


To make the 154 card emit stepping pulses you send a one-word setting to the front end. This word contains a count of the number of steps. If this word is positive, then the 154 card raises the UP control line, if this word is negative then the 154 card raises the DOWN line. The word you send to Dec-P is a two's complement integer, i.e. ordinary negative numbers that are used in computer arithmetic. To move up 100 steps send a +100, to move down 100 steps send a -100.

The writeup for the card seems to indicate that it wants a signed magnitude form of number. Dec-P performs this conversion for you.

Sending settings to the card does not affect the state of the Polarity bit.

When you "read the setting", not a particularly valuable exercise, you get the current value in the counter.

The scaling information entered into the data base for this property should show that it is a stepping motor, and can look just like the scaling for the 057 stepping motors. The length of the setting property is 2 bytes.


You transmit 1 word to Dec-P with one of the following codes to excercise basic control operations:

Code Camac Function Operation
1 F(28)A(0) OFF
2 F(30)A(0) ON
3 F(12)A(0) RESET
4 F(16)A(0) POLARITY +
5 F(16)A(0) POLARITY -

All of these operations translate into relay contact closures to operate an external power supply.

The scaling block for the basic control property should be set up to scale the above list of functions to the above codes.


It is not clear to me how the 4 bits of external status are returned by the 057 card when you perform the F(0)A(1) status read. In any case I have set up the basic status word with the polarity bit in the high order bit, and the low order byte of the status read in the low order byte of the basic status word. If we ever hook up a 154 to a power supply this arrangement ought to work, but the meaning of the bits would need to be documented.

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