Software Handshaking - Motorola symbol ds9808 Reference Manual

7 - 12 Symbol DS9808 Product Reference Guide

Software Handshaking

This parameter offers control of the data transmission process in addition to, or instead of, that offered by hardware
handshaking. There are five options.
If software handshaking and hardware handshaking are both enabled, hardware handshaking takes precedence.
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None: Select this to transmit data immediately. The digital scanner expects no response from the host.
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ACK/NAK: If you select this option, after transmitting data, the digital scanner expects either an ACK or NAK
response from the host. When it receives a NAK, the scanner transmits the same data again and waits for
either an ACK or NAK. After three unsuccessful attempts to send data after receiving NAKs, the digital
scanner issues an error indication and discards the data.
The digital scanner waits up to the programmable Host Serial Response Time-out to receive an ACK or NAK.
If the scanner does not get a response in this time, it issues an error indication and discards the data. There
are no retries when a time-out occurs.
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ENQ: If you select this option, the digital scanner waits for an ENQ character from the host before
transmitting data. If it does not receive an ENQ within the Host Serial Response Time-out, the digital scanner
issues an error indication and discards the data. The host must transmit an ENQ character at least every
Host Serial Response Time-out to prevent transmission errors.
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ACK/NAK with ENQ: This combines the two previous options. For re-transmissions of data, due to a NAK
from the host, an additional ENQ is not required.
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XON/XOFF: An XOFF character turns the digital scanner transmission off until the scanner receives an XON
character. There are two situations for XON/XOFF:
• The digital scanner receives an XOFF before has data to send. When the scanner has data to send, it
waits up to Host Serial Response Time-out for an XON character before transmission. If it does not
receive the XON within this time, the digital scanner issues an error indication and discards the data.
• The digital scanner receives an XOFF during a transmission. Data transmission then stops after sending
the current byte. When the digital scanner receives an XON character, it sends the rest of the data
message. The digital scanner waits indefinitely for the XON.