Link Characteristics; Basic Operating Modes; Free Flow - IBM 4685-L0D Setup, Operation, And Service Manual

Link characteristics

This section describes the following link characteristics of the RS-232 scanner inter-
face:

Basic operating modes

The RS-232 scanner interface operates in any of the following modes:

Free flow

In the free-flow operating mode, the conditions are as follows:
Free flow with timing and flow control
In this operating mode, there is no handshake capability. The operation proceeds
as follows:
For the details of the free-flow operating mode, see Figure 4-1.
Basic operating modes
Message timing
Error detection
Free-flow operating mode
Software-flow operating mode
Hardware-flow operating mode
Inter-character delay operating mode
When the scanner receives the DTR signal, it establishes a connection with a
POS terminal, and enters the ready state.
The scanner decodes the labels immediately after power on.
The scanner optionally buffers one additional label.
The scanner sends the RTS signal, and then requests that the decoded data
from the label be sent to the POS terminal.
The scanner uses the intercharacter delay that has been configured.
The scanner decodes a label. If you have chosen beep/lamp option 1, the
scanner beeps and the lamp comes on. (For a description of the beep/lamp
function, see page 4-16) The RTS signal is issued to notify the POS terminal
that the scanner is ready to transmit data.
The scanner begins transmitting data.
As soon as the last character of the message has been transmitted, the RTS
signal is resent. If you have chosen beep/lamp option 2, the scanner beeps
and the lamp comes on.
Another label is decoded, to begin a repetition of the cycle.
Chapter 4. RS-232 Scanner interface specifications
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