Siemens AS 235 Configuring, Standard function blocks, Blocks for analog and digital processing

This catalog is out of date, see note on page 1

System architecture

Configuring

Standard function blocks

Standard function blocks

￿Dedicated function blocks are present in the automation sys- tems to solve the control tasks. These are the so-called standard function blocks. The AS 235, AS 235 H and AS 235 K systems have the same standard function blocks for data acquisition, closed-loop and open-loop control, calculation and monitoring.

The standard function blocks present in the system software are activated by engineering tools using configuring instructions. The blocks are combined into an automation structure which is processed cyclically, and sometimes acyclically, by the central processor of the automation system.

The configuration of the automation structure is usually gener- ated graphically using the PROGRAF AS+ configuring tool (see also page 2/9).

The following tables list the standard function blocks divided according to their areas of application.

Blocks for analog and digital processing

Type	Designation	Function
SUM	Adder	Y = X1 + X2 - X3 - X4
MUL	Multiplier	Y = X1 · X2
DIV	Divider	Y = X1/X2
RAD	Square-root extractor	Y = X or Y = K X
LN	Logarithm extractor	Y = KF · Ioge X
EXP	Exponential value	Y = ex
ABS	Absolute value	X = X
INT	Integrator	Y = K · ∫	X dt, K = 1/T
DIF	Differentiator	Y(s)/X(s) = (T·s)/(1 + (T·s/v))
￿PT
	Delay	Y(s)/X(s) = 1/(1 + T·s)
TOZ	Dead time	Y(s)/X(s) = e-s·T
MIN	Minimum-value	Y = minimum of X1, X2, X3
	selector
MAX	Maximum-value	Y = maximum of X1, X2, X3
	selector
TOB	Dead band	Y = X-TOBU for X < TOBU
		0	for TOBU ≤X ≤TOBO
		X-TOBO for X > TOBO
PLG	Function generator	Linear interpolation between 6
		pairs of turning points
GW	Limit monitor	Limit check between two switch-
		ing points
ASL	Analog-value switch	Y = X1 for S = “0”
		Y = X2 for S = “1”
SPEI	Analog-value mem-	Storage of up to 256 analog val-
	ory	ues

Blocks for binary processing

￿
	Designation
Type
VU	AND
VO	OR
VN	Negation
VM	Flag
VZ	Time delay
VS + STEP	STEP M block
MPX	Multiplexer
BW	Binary selection
INKU	Incremental con-
	verter
BCE	BCD input
BCA	BCD output
KA	Sequence start
KAK
KB	Sequence
KBK
KS	Sequence step
KV
	Sequence branch
KE	Sequence end
KEK
HA	Auxiliary oil auto-
	matic unit
HUP	Horn block
EAR	Individual analog-
	value allocation
EBR	Single-bit allocation
UBR	Universal binary
	location

Function

A = E1 ∧ E2 ∧ E3

A = E1 ∨ E2 ∨ E3

A = E

Flag of binary input signals (flip- flop)

Switch-on and switch-off delays

Freely programmable in STEP M

To supply the STEP commands in the following VS/KS block

Selection of status combination from up to 3 binary signals

Converts analog value into an open or close pulse

Conversion of a BCD signal into an analog value

Conversion of an analog value into a BCD signal

Marks the start of an ON/OFF branch of a subgroup control

As KA, but with additional func- tions

Conditions of a control step, for power plants

As KB, but with additional func- tions

As KB, for process plants

Branch of a sequence into a max- imum of 6 branches, with process plants

Last block in a sequence

As KE, but with additional func- tions

Controls electric auxiliary oil pumps for oil supply to generator sets

Triggers signalling equipment (optical and audible)

Allocates analog values from out- puts in GA blocks

Links individual binary outputs to GB/GM data blocks

Links 16 binary outputs to GB/ GM data blocks

Siemens PLT 111 · 1999 2/5