VI_ATTR_ASRL_FLOW_CNTRL

NI-VISA 15.0 Help

Edition Date: June 2015

Part Number: 370131S-01

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Resource Classes

Serial INSTR

Attribute Information

Access Privilege Data Type Range Default

Read/Write
Global

ViUInt16

VI_ASRL_FLOW_NONE (0)
VI_ASRL_FLOW_XON_XOFF (1)
VI_ASRL_FLOW_RTS_CTS (2)
VI_ASRL_FLOW_DTR_DSR (4)

VI_ASRL_FLOW_NONE

Description

VI_ATTR_ASRL_FLOW_CNTRL indicates the type of flow control used by the transfer mechanism.

  • If this attribute is set to VI_ASRL_FLOW_NONE, the transfer mechanism does not use flow control, and buffers on both sides of the connection are assumed to be large enough to hold all data transferred.
  • If this attribute is set to VI_ASRL_FLOW_XON_XOFF, the transfer mechanism uses the XON and XOFF characters to perform flow control. The transfer mechanism controls input flow by sending XOFF when the low-level I/O receive buffer is nearly full, and it controls the output flow by suspending transmission when XOFF is received.
  • If this attribute is set to VI_ASRL_FLOW_RTS_CTS, the transfer mechanism uses the RTS output signal and the CTS input signal to perform flow control. The transfer mechanism controls input flow by unasserting the RTS signal when the low-level I/O receive buffer is nearly full, and it controls output flow by suspending the transmission when the CTS signal is unasserted.
  • If this attribute is set to VI_ASRL_FLOW_DTR_DSR, the transfer mechanism uses the DTR output signal and the DSR input signal to perform flow control. The transfer mechanism controls input flow by unasserting the DTR signal when the low-level I/O receive buffer is nearly full, and it controls output flow by suspending the transmission when the DSR signal is unasserted.

This attribute can specify multiple flow control mechanisms by bit-ORing multiple values together. However, certain combinations may not be supported by all serial ports and/or operating systems.


Related Topics

Controlling the Serial I/O Buffers

INSTR Resource

VI_ATTR_ASRL_BAUD

VI_ATTR_ASRL_DATA_BITS

VI_ATTR_ASRL_PARITY

VI_ATTR_ASRL_STOP_BITS

VI_ATTR_ASRL_XOFF_CHAR

VI_ATTR_ASRL_XON_CHAR

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