
1-10 Programming Guide
Preparing for Use ESG Family Signal Generators
Overview of Serial Interface (RS-232) Programming
Overview of Serial Interface (RS-232) Programming
Serial interface programming techniques are similar to most general I/O applications. The
interface card is initialized by use of CONTROL statements; STATUS statements evaluate
its readiness for use. Data is transferred between the desktop computer and a peripheral
device by OUTPUT and ENTER statements.
Due to the asynchronous nature of serial I/O operations, special care must be exercised to
ensure that data is not lost by sending to another device before the device is ready to
receive. Modem line handshaking can be used to help solve this problem. These and other
topics are discussed in greater detail elsewhere in this chapter.
Determining Operating Parameters
Before you can successfully transfer information to a device, you must match the operating
characteristics of the interface to the corresponding characteristics of the peripheral
device. This includes matching signal lines and their functions as well as matching the
character format for both devices.
Handshake and Baud Rate
To determine hardware operating parameters, you need to know the answer for each of the
following questions about the peripheral device:
• Which of the following signal and control lines are actively used during communication
with the peripheral?
— Data Set Ready (DSR)
— Clear to Send (CTS)
• What baud rate (line speed) is expected by the peripheral?
Character Format Parameters
To define the character format, you must know the requirements of the peripheral device
for the following parameters:
• Character Length: Eight data bits are used for each character, excluding start, stop, and
parity bits.
• Parity Enable: Parity is disabled (absent) for each character.
• Stop Bits: One stop bit is included with each character.
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