TBASIC Integer Constants, Variables & Operators

The TBASIC compiler in TRiLOGI Version 5 supports full 32-bit integer computations. However, only variable A to Z are 32 bits in length which allow them to represent number between -231 to -231, the remaining system variables and data memory DM[n] are all 16-bit variables which means that they can only store number between -32768 to +32767. However, all numerical computations and comparisons in TBASIC are carried out in 32-bit signed integer, regardless of the bit-length of the variables involved in the numerical expression.

1.     Integer Constants

These may be entered directly in decimal form, or in hexadecimal form by prefixing the number with the symbol "&H". e.g.

12345678
&H3EF =1007 (decimal)

If the result of an expression is outside the 32-bit limits, it will overflow and change sign. Care must therefore be exercised to prevent unexpected result from an integer-overflow condition.

A constant may be used in an assignment statement or in an expression as follow:

A = 12345
IF A*30 + 2345/123 > 100
THEN ....ENDIF

IMPORTANT (16-bit variables comparison)

When entering an integer constant using the hexadecimal prefix "&H", it is important to note the sign of the intended value and extend the signs to most significant bit of the 32 bit expression. E.g. to represent a decimal number "-1234", the hexadecimal representation must be "&HFFFFFB2E" and not "&HFB2E".

Assuming that a 16-bit variable DM[1] contains the number -1234 and a comparison statement is made to check if the number is -1234. The 32-bit hexadecimal representation of constant -1234 is &HFFFFFB2E. If you enter the constant as 16-bit representation "&HFB2E" as follow:

IF DM[1] <> &HFB2E CALL 5

TBASIC translates the number "&HFB2E" into a 32-bit decimal number 64302, which when compared to the number "-1234" contained in DM[1] will yield a "False" result which is an error. The following are the correct representation:

a) IF DM[1] <> -1234 CALL 5 : ENDIF
b) IF DM[1] <> &HFFFFFB2E" CALL 5: ENDIF

2.     Integer variables:

Variables are memory locations used for storing data for later use. All Integer variables used in TBASIC are GLOBAL variables - this means that all these variables are shared and accessible from every custom function.

TBASIC supports the following integer variables:

  1. 26 Integer variables A, B, C....Z which are 32-bit variables. Note that the variable name must be a single character.

  2. A large, one-dimensional 16-bit integer array from DM[1] to DM[4000], where DM stands for Data Memory. A DM is addressed by its index enclosed between the two square brackets "[" and "]". e.g. DM[3], DM[A+B*5], where A and B are integer variables.

  3. System variables. These are special integer variables which relates to the PLC hardware, as follow:

Inputs, Outputs, Relays, Timers and Counters Contacts

The bit addressable I/Os elements are organized into 16-bit integer variables INPUT[n], OUTPUT[n], RELAY[n], TIMERBIT[n] and CTRBIT[n] so that they may be easily accessed from within a CusFn. These I/Os are arranged as shown in the following diagram:

systemvariable.gif (4712 bytes)

Timers and Counters Present Values

The present values (PV) of the 128 timers and 128 counters in the PLC can be accessed directly as system variables:

timerPV[1] to timerPV[256], for timers' present value

ctrPV[1] to ctrPV[256], for counters' present value

DATE and TIME Variables

The PLC's Real-Time-Clock (RTC) derived date and time can be accessed via variables DATE[1] to DATE[3] and TIME[1] to TIME[3], respectively as shown in the following table:

Date

Time

YEAR

DATE[1]

HOUR

TIME[1]

MONTH

DATE[2]

MINUTES

TIME[2]

DAY

DATE[3]

SECOND

TIME[3]

Day of Week

DATE[4]

    

DATE[1] : may contain four digits (e.g. 1998, 2003 etc).
DATE[4] : 1 for Monday, 2 for Tuesday, .... 7 for Sunday.

High Speed Counters

The M-series PLC support High Speed Counters (HSC) which can be used to capture high frequency incoming pulses from positional feedback encoder. These high speed counters are accessible by CusFn using the variables HSCPV[1] to HSCPV[8]. All HSCPV[n] are 32-bit integer variables.

Special Variables - Used by EMIT.

4 x  special 16 bit integer variables:  EMEVENT[1] to EMEVENT[4] - emEvent[1] is also used for email purpose.

16 x  16-bit integer variables:  EMINT[1] to EMINT[16]

16 x  32-bit integer variables:  EMLINT[1] to EMLINT[16]

3.     Integer operators:

"Operators" perform mathematical or logical operations on data. TBASIC supports the following integer operators:

i) Assignment Operator: An integer variable (A to Z, DM and system variables, etc) may be assigned a value using the assignment statement:

A = 1000
X = H*I+J + len(A$)

ii) Arithmetic Operators:

Symbol

 Operation

Example

+

Addition

A = B+C+25

-

Subtraction

Z = TIME[3]-10

*

Multiplication

PRINT #1 X*Y

/

Division

X = A/(100+B)

MOD

Modulus

Y = Y MOD 10

iii) Bitwise Logical Operators: logical operations is perform bit-for-bit between two 16-bit integer data.

Symbol

 Operation

Example

&

logical AND

IF input[1] & &H02 ...

|

logical OR

output[1] = A | &H08

^

Exclusive OR

A = RELAY[2] ^ B

~

logical NOT

A = ~timerPV[1]

iv) Relational Operators : Used exclusively for decision making expression in statement such as IF expression THEN ..... and WHILE expression ....

Symbol

 Operation

Example

=

Equal To

IF A = 100

<>

Not Equal To

WHILE CTR_PV[0]<> 0

>

Greater Than

IF B > C/(D+10)

<

Less Than

IF TIME[3] < 59

>=

 Greater Than or Equal To

WHILE X >= 10

<=

 Less Than or Equal To

IF DM[I] <= 5678

AND

 Relational AND

IF A>B AND C<=D

OR

 Relational OR

IF A<>0 OR B=1000

v) Functional Operators : TBASIC supports a number of built in functions which operate on integer parameters as shown below:

ABS(n), ADC(n), CHR$(n), HEX$(n), STR$(n)

For detailed explanation of these functions please refer to the next chapter: "Programming Language Reference"

4.     Hierachy of Operators

The hierarchy of operators represent the priority of computation. Eg. X = 3 + 40*(5 - 2). The compiler will generate codes to compute 5 - 2 first because the parentheses has the higher hierarchy, the result is then multiplied by 40 because multiplication has a higher priority then addition. Finally 3 will be added to the result. If two operators are of the same hierarchy, then compiler will evaluate from left to right. e.g. X = 5 + 4 - 3. 5+4 is first computed and then 3 will be subtracted. The following table list the hierarchy of various operator used.

Hierarchy

Symbol

Descriptions

Highest

( )

Parentheses
 

*, / , MOD

Multiplication/Division
 

+, -

Add/Subtract
 

-

Negate
 

&, |, ^,~

Logical AND,OR,XOR,NOT

Lowest

=,<>,>,>=,<,<=

Relational operators

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