Motorola LS4208 用户手册
6 - 12 Symbol LS4208 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.
handshaking. There are five options.
If Software Handshaking and Hardware Handshaking are both enabled, Hardware Handshaking takes
precedence.
precedence.
•
None: When this option is selected, data is transmitted immediately. No response is expected from host.
•
ACK/NAK: When this option is selected, after transmitting data, the scanner expects either an ACK or NAK
response from the host. When a NAK is received, the scanner transmits the same data again and waits for
either an ACK or NAK. After three unsuccessful attempts to send data when NAKs are received, the scanner
issues an error indication and discards the data.
response from the host. When a NAK is received, the scanner transmits the same data again and waits for
either an ACK or NAK. After three unsuccessful attempts to send data when NAKs are received, the scanner
issues an error indication and discards the data.
The 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.
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.
•
ENQ: When this option is selected, the scanner waits for an ENQ character from the host before transmitting
data. If an ENQ is not received within the Host Serial Response Time-out, the 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.
data. If an ENQ is not received within the Host Serial Response Time-out, the 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.
•
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.
from the host, an additional ENQ is not required.
•
XON/XOFF: An XOFF character turns the scanner transmission off until the scanner receives an XON
character. There are two situations for XON/XOFF:
character. There are two situations for XON/XOFF:
•
XOFF is received before the scanner 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 the XON is not received
within this time, the scanner issues an error indication and discards the data.
Host Serial Response Time-out for an XON character before transmission. If the XON is not received
within this time, the scanner issues an error indication and discards the data.
•
XOFF is received during a transmission. Data transmission then stops after sending the current byte.
When the scanner receives an XON character, it sends the rest of the data message. The scanner waits
up to 30 seconds for the XON.
When the scanner receives an XON character, it sends the rest of the data message. The scanner waits
up to 30 seconds for the XON.