Online Development Notebook > Index > Programming Overview > Device Commands > WriteB

WriteB - Write byte value to port B


Description:

This is a function that writes a byte value to port B when the port is set as an output. The possible values range from 0-255 (00h to FFh).

Command Syntax: (USBm.dll)

USBm_WriteB( device, data )

The USBm_WriteB function syntax has these parts:

Description Description
device A zero-based index to address the appropriate USB device.
data Byte to write to Port B.

Remarks:

Port B does not have to have all 8 bits set to output for this to work. You can have a mix of inputs and outputs on the port and this command will set high or low only those lines that are output.


VB Declaration

Public Declare Function USBm_WriteB _
    Lib "USBm.dll" _
        (ByVal device As Byte, _
        ByVal data As Byte) _
    As Integer

VB Example

USBm_WriteB 7, &H0F

This code fragment writes the value of &H0F to port B of device 7.


C Prototype

int USBm_WriteB( unsigned char device, unsigned char data );

C Example


RobotBASIC

usbm_WriteB(ne_DeviceNumber,ne_ByteValue)

Returns true if successful, false otherwise. The byte value is written to Port A⁄B.


Raw Command Format:

Byte Number Description
0 02h: WriteBCmd
1 Byte Data - This byte is written to port B, D8 - D15
The most significant bit of the byte value is written to D15
2 <not used>
3 <not used>
4 <not used>
5 <not used>
6 <not used>
7 <not used>

Raw Command Format Details:

Byte 0 contains the command. Byte 1 contains the data to write to port B. Byte 2 through byte 7 are unused.

Raw Command Response Format:

Byte Number Description
0 02h: WriteBCmd
1 <not used>
2 <not used>
3 <not used>
4 <not used>
5 <not used>
6 <not used>
7 <not used>

Raw Command Response Format Details:

Byte 0 contains the command. Byte 1 through byte 7 are unused.

Raw Command Example Usage:

Writing a 11h to port B with the command 02-11-00-00-00-00-00-00 will set lines B.4 and B.3 high and will set the remainder of the lines low, assuming that they are configured as outputs.


Hardware:  U401 USB Interface    U421 USB Interface   U451 USB Interface

Programming:  USBm DLL Programming    Download Files

Application Notes:  U4x1 Application Notes    Misc Applications and Information    FAQ

While every effort has been made to make sure that the information posted on this site is correct, the author can not be held liable for any damages whatsoever for losses as a result of the application of this information. Use this information at your own risk.

USBmicro can design your custom and semi-custom USB product. Email about USB design can be directed to " Robert " at usbmicro.com.

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