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1257 User Manual
Computer Interfaces 4-18
EADS North America Defense
Test and Services, Inc.
©
2001
Setting the Flow
Control Option
Description
Flow control is a means by which the data terminal (or host
computer acting as a terminal) may pace the flow of data coming
from the 1257 so that the terminal has time to properly receive the
data. It also allows the 1257 to pace commands coming from the
terminal so that the 1257 has sufficient time to execute the
commands as they arrive.
The 1257 provides three flow control options:
•
XON/XOFF: Software flow control.
The RS-232 device that is
receiving data may send an XOFF character (ASCII 19
10
) to the
sending device, commanding the sending device to suspend
data output. Later, when the receiving device is ready for more
data, it may send an XON character (ASCII 17
10
) to the
sending device, indicating that data transmission may be
resumed.
•
CTS/RTS: Hardware flow control.
The 1257 normally holds
the RS-232 Clear-To-Send (CTS) line in the TRUE state (-12
volts). When the 1257 is receiving data, and needs to have
data transmission suspended, it takes the CTS line to the
FALSE state (+12 volts). When it is ready for more data, it
returns the CTS line to the TRUE state. Similarly, the data
terminal uses the RS-232 Request-To-Send (RTS) line to pace
data coming from the 1257. The data terminal normally holds
the RTS line in the TRUE (-12 volts) state. To suspend data
from the 1257, it takes the RTS signal to the FALSE state (+12
volts). To resume data transfer, the terminal takes the RTS
signal TRUE again.
•
Disabled: No flow control.
If your terminal does not support
flow control, set the 1257 to disable flow control. Note that
sending large blocks of data without flow control may
necessitate a slower baud rate to avoid data overrun problems.
Setting the Flow Control Option
To select the flow control option, or to disable flow control, proceed
as follows:
1. Press the top key. Rotate the knob until the top line reads:
>-----SETTINGS-----<
2. Select line 2 (next to top line) by pressing the second key. This
selects line 2: