oFeedBack4 Object

Description
Operation
Properties

Examples
Connections
Related
Version History & Bug list

The oFeedBack4 Object is an I/O Function Object that reads a 4 x 4 matrix feedback loop. If feedback is detected on any one of the 16 possible paths, the signal and receiver of the path is reported.

The following table lists the size and availability of the oFeedBack4 Object.

	Object	Size	Description	A1	A2	B1	B2	C1
	oFeedBack4	4 Bytes	Reads a 4 x 4 matrix feedback loop.	x	x	x	x	x

Operation:

An oFeedBack4 Object splits I/O Group 1 (I/O lines 8 - 15) into 2 sets of 4 I/O lines and uses them to form a 4 by 4 feedback matrix. The least significant 4 I/O Lines are used to send signals and the most significant 4 I/O Lines are used to detect the feedback.

The 4 signal lines are individually and sequentially set low (0-Volts) while the 4 feedback lines are used to detect any feedback from those signals. Feedback is detected when any one of the 4 feedback lines detects the signal being sent out by the signal lines. The oFeedBack4 Object handles all the required I/O logic. The 4 x 4 matrix requires no isolation diodes or pull up resistors for operation.

When the Operate property is set to 1 the internal pull-up resistors on I/O lines 8 - 15 are activated and the 4 x 4 feedback matrix is scanned. If any outgoing signal is detected on the feedback lines, the Result property is updated with a value and the "Any" property is set to 1.

The value of the Result property is calculated by (((signal - 1) * 4) + (feedback-1)). If feedback is detected on two lines simultaneously the result with the highest value will be used. The "Any" property will remain at 1 so long as at least 1 feedback is detected. If a second feedback is detected before the first is lost, then the Result and "Any" property will remain unchanged from the values set at the time of the first feedback. Once all feedback is lost, the "Any" property is be cleared to 0.

When the Operate property is set to 0 the feedback matrix scanning is suspended until the Operate property is set back to 1.

Properties:

The following table lists the properties of the oFeedBack4 Object:

Property
Description

Result

A value that indicates the path where feedback was detected.

Object Class: oByte Value Range: 0 - 15

Data Type: Numeric (Read-Only) Default Value: 0

The Result is calculated as (((signal - 1) * 4) + (feedback-1))

Any

A value that indicates that feedback was detected on any one or more feedback path.

Object Class: oLogic Value Range: 0 - 1

Data Type: Numeric Default Value: 0

Any Description

0 None of the feedback paths are returning signals.

1 Any one or more feedback path is returning a signal.

IOGroup

I/O Group 1 used to read and drive the feedback loops.

Object Class: oIOGroup Value Range: 1

Data Type: Numeric (Read-Only) Default Value: 1

Operate

A value that selects whether or not the feed back loops are being tested.

Object Class: oOperate Value Range: 0 - 1

Data Type: Numeric Default Value: 0

Operate Constant Description

0 cvOff
The feedback feed back loops are not being tested.

1 cvOn
The feedback feed back loops are being tested.

Address

Returns a pointer to the address of the oCounter Object instance.

Object Class: oAddress Value Range: 0 - 127

Data Type: Pointer (Read Only) Default Value: Address of Object

Examples:

In the following example, the oFeedBack4 Object is used.

Visual Basic Syntax

C and Java Syntax

'This program reads a 4x4 matrix and
'outputs the value to I/O lines 8 - 15.

Dim A As New oFeedBack4
Dim D As New oDIO1
Dim C As New oDIO8

Sub Main()
  C.IOGroup = 3
  C.Direction = cvOutput
  D.IOLine = 7
  D.Direction = cvOutput
  A.Operate = 1
  Do
    C = A.Value
    D = A.Any
  Loop
End Sub

// This program reads a 4x4 matrix and
// outputs the value to I/O lines 8 - 15.

oFeedBack4 A = New oFeedBack4;
oDIO1 D = New oDIO1;
oDIO8 C = New oDIO8;

Void Main(Void){
  C.IOGroup = 3;
  C.Direction = cvOutput;
  D.IOLine = 7;
  D.Direction = cvOutput;
  A.Operate = 1;
  Do{
    C = A.Value;
    D = A.Any;
  } While (1);
}

Basic Syntax

'This program reads a 4x4 matrix and
'outputs the value to I/O lines 8 - 15.

A As oFeedBack4(cvOn)
D As oDIO1(7,cvOutput)
C As oDIO8(3,cvOutput)

Do
  C = A.Value
  D = A.Any
Loop

Connections:

See the oKeypad or oKeypadP Object for connections.