Specifications

Chapter 2 23
Programming Command Guidelines
Getting Started with Programming Commands
2. Programming Command
Guidelines
Character Format Parameters
To define the character format, you must know the requirements of the peripheral
device for the following parameters:
• Data Length: Eight data bits are used for each character, excluding start, stop,
and parity bits.
• Stop Bits: One stop bit is included with each character.
• Parity: Parity is disabled (absent) for each character.
Modem Line Handshaking
To use modem line handshaking for data transfer, set the Request-to-Send (RTS)
and Clear-to-Send (CTS) modem lines to active state on your controller.
Setting Xcontrol to Xon/Xoff allows the Test Set to stop data transmission from
the controller when the buffer of the Test Set is full and then start it again when the
Test Set is ready.
Data Transfer Errors
The serial interface can generate several types of errors when certain conditions
are encountered while receiving data from the peripheral device. Errors can be
generated by any of the following conditions:
• Parity error. The parity bit on an incoming character does not match the parity
expected by the receiver. This condition is most commonly caused by line
noise.
• Framing error. Start and stop bits do not match the timing expectations of the
receiver. This can occur when line noise causes the receiver to miss the start bit
or obscures the stop bits.
• Overrun error. Incoming data buffer overrun caused a loss of one or more data
characters. This is usually caused when data is received by the interface, but no
ENTER statement has been activated to input the information.
• Break received. A BREAK was sent to the interface by the peripheral device.
The computer program must be able to properly interpret the meaning of a
break and take appropriate action.