Instruction manual

Unsigned Compares

890USE18300 September 2003

Operational

Input

An inside-the-window compare block uses one operational input. It must be a word

with an unsigned integer in the range 0 to 65 535. The input can come from:

an analog input from a module on the island

an analog output from the virtual module (See The Virtual Module, p. 28)

if the less-than-threshold compare is the second block in a nested reflex action

(See Nesting Two Reflex Blocks, p. 36), the operational input may be configured

as the output of the first reflex block

Suppose that you have two threshold values, where TH 1 = 30 000 and

TH 2 = 40 000. Then suppose that the operational input is 32 000 and ∆ =0:

Because the value of the operational input falls inside the window defined by TH 1

and TH 2, the block produces a Boolean 1 as its output.

Note: Unsigned compare blocks are often nested together with counter blocks

(See Counter Reflex Blocks, p. 93). The unsigned compare is always the second

block in the nested action, and the analog output from the counter is used as its

operational input. These two action types complement each other well because the

output from a counter is always unsigned with 16-bit resolution.

Note: Do not use a word that contains a signed negative integer value as the

operational input to an unsigned integer compare. The block will misinterpret a

value of 1 in the sign bit position (bit 15) as part of the integer value. Avoid the use

of modules such as the STB AVI 1270 analog input module, which produce an

input with a possible negative integer value, as the source for the operational input

to the block.

30 000 (TH 1)

40 000 (TH 2)

65 535

32 000