5-7
check methods (checksum and CRC), and error packet retransmission mechanism (generally the
maximum number of retransmission attempts is ten).
The Xmodem transmission procedure is completed by the cooperation of a receiving program and a
sending program. The receiving program sends a negotiation character to negotiate a check method.
After the negotiation, the sending program starts to send data packets. Upon receiving a complete
packet, the receiving program checks the packet using the agreed method.
z
If the check succeeds, the receiving program sends an ACK character and the sending program
proceeds to send the next packet.
z
If the check fails, the receiving program sends a NAK character and the sending program
retransmits the packet.
Modifying serial communication parameters
To save the upgrade time, a high serial port baud rate is preferred; to ensure the transmission reliability,
the baud rate needs to be reduced.
Follow these steps to change the serial communication baud rate:
1) Enter the BootWare main menu and select
2
to enter the serial interface submenu. Then, select
5
in the submenu. The system displays the following:
=================================<BAUDRATE SET>=============================
|Note:'*'indicates the current baudrate |
| Change The HyperTerminal's Baudrate Accordingly |
|---------------------------<Baudrate Avaliable>---------------------------|
|<1> 9600(Default)* |
|<2> 19200 |
|<3> 38400 |
|<4> 57600 |
|<5> 115200 |
|<0> Exit |
============================================================================
Enter your choice(0-5):
2) Select an appropriate baud rate. For example, select
5
for 115200 bps. The following information
appears:
Baudrate has been changed to 115200 bps.
Please change the terminal's baudrate to 115200 bps, press ENTER when ready.
Now that the serial interface baud rate of the LSQM1WCMB0 has been changed to 115,200 bps while
that of the terminal is still 9,600 bps, the LSQM1WCMB0 access controller module and the terminal
cannot communicate with each other. For this reason, you need to change the baud rate to 115,200 bps
in HyperTerminal.
3) Disconnect the terminal connection in HyperTerminal, as shown below:
Figure 5-2
Disconnect the terminal connection
