Data Communications

Flow Control

The CodeWriter 4500 Series printers provide two methods to control the flow of data between the host system and the printer. Hardware or Xon/Xoff flow control is selected from the Operator Panel.

Hardware Flow Control

The printer uses the CTS, RTS, DTR, and DSR signals during hardware flow control. Table 4 lists how the printer uses each signal.

Signal

Function

CTS

Input: The printer monitors the CTS signal for requests

 

from the host system to send data. This signal must be

 

asserted ON (Spacing, Positive Voltage) for the printer to

 

receive data.

RTS

Output: The printer asserts this signal ON (Spacing,

 

Positive Voltage) whenever the printer is turned on. The

 

polarity of this signal may be changed from the Operator

 

Panel.

DTR

Output: The printer asserts this signal ON (Spacing,

 

Positive Voltage) whenever it is ready to receive data. This

 

signal controls the flow of data from the host system.

 

When the printer’s input buffers have reached an almost

 

full level, the printer de-asserts the signal OFF (Marking,

 

Negative). In this condition host system should suspend

 

sending data. The polarity of this signal may be changed

 

from the Operator Panel.

DSR

Input: The printer monitors the DSR signal to control

 

sending data to the host system. This signal must be

 

asserted ON (Spacing, Positive Voltage) for the printer to

 

send data. The CodeWriter 4500 Series printers depend

 

on data transmission to the host system for many

 

applications.

Table 4 - Hardware Flow Control Signal Functions

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AMT Datasouth 4500 Series manual Hardware Flow Control