# Transfer Fcn Direct Form II

Implement Direct Form II realization of transfer function

• Library:
• Simulink / Additional Math & Discrete / Additional Discrete

## Description

The Transfer Fcn Direct Form II block implements a Direct Form II realization of the transfer function that the Numerator coefficients and Denominator coefficients excluding lead parameters specify. The block supports only single input-single output (SISO) transfer functions.

The block automatically selects the data types and scalings of the output, the coefficients, and any temporary variables.

## Ports

### Input

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Input signal, specified as a scalar or vector.

Data Types: `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64` | `fixed point`

### Output

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Output signal, specified as a scalar or vector.

Data Types: `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64` | `fixed point`

## Parameters

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Specify the numerator coefficients as a vector.

#### Programmatic Use

 Block Parameter: `NumCoefVec` Type: character vector Values: vector Default: `'[0.2 0.3 0.2]'`

Specify the denominator coefficients, excluding the leading coefficient, which must be `1.0`.

#### Programmatic Use

 Block Parameter: `DenCoeffVec` Type: character vector Values: vector Default: `'[-0.9 0.6]'`

Specify the initial condition as a scalar.

#### Programmatic Use

 Block Parameter: `vinit` Type: character vector Values: scalar Default: `'0.0'`

Specify the rounding mode for fixed-point operations. For more information, see Rounding (Fixed-Point Designer).

#### Programmatic Use

 Block Parameter: `RndMeth` Type: character vector Values: ```'Ceiling' | 'Convergent' | 'Floor' | 'Nearest' | 'Round' | 'Simplest' | 'Zero'``` Default: `'Floor'`

When you select this check box, overflows saturate to the maximum or minimum value that the data type can represent. Otherwise, overflows wrap.

When you select this check box, saturation applies to every internal operation on the block, not just the output or result. In general, the code generation process can detect when overflow is not possible. In this case, the code generator does not produce saturation code.

#### Programmatic Use

 Block Parameter: `DoSatur` Type: character vector Values: `'off' | 'on'` Default: `'off'`

## Block Characteristics

 Data Types `double` | `fixed point` | `integer` | `single` Direct Feedthrough `no` Multidimensional Signals `no` Variable-Size Signals `no` Zero-Crossing Detection `no`

## Version History

Introduced before R2006a