|Online Development Notebook > Index > Programming Overview > Device Commands > WriteA|
WriteA - Write byte value to port A
This is a function that writes a byte value to port A when the port is set as an output. The possible values range from 0-255 (00h to FFh).
Command Syntax: (USBm.dll)
USBm_WriteA( device, data )
The USBm_WriteA function syntax has these parts:
|device||A zero-based index to address the appropriate USB device.|
|data||Byte to write to Port A.|
Port A 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.
|Public Declare Function USBm_WriteA _|
Lib "USBm.dll" _
(ByVal device As Byte, _
ByVal data As Byte) _
|USBm_WriteA 3, &H55|
This code fragment writes the value of &H55 to port A of device 3.
|int USBm_WriteA( unsigned char device, unsigned char data );|
Returns true if successful, false otherwise. The byte value is written to Port A⁄B.
Raw Command Format:
|1||Byte Data - This byte is written to port A, D0 - D7
The most significant bit of the byte value is written to D7
Raw Command Format Details:
Byte 0 contains the command. Byte 1 contains the data to write to port A. Byte 2 through byte 7 are unused.
Raw Command Response Format:
Raw Command Response Format Details:
Byte 0 contains the command. Byte 1 through byte 7 are unused.
Raw Command Example Usage:
Writing a E7h to port A with the command 01-E7-00-00-00-00-00-00 will set A.7, A.6, A.5, A.2, A.1, and A.0 high and will set lines A.4 and A.3 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
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