WIT2450
©
2000- 2005 Cirronet
™
Inc
21
M-2450-0000 Rev B
Bytes, Baud Rate and Hop Time
When Store and Forward mode is entered, through the wb command, the remote
packet length is set to the maximum value, the packet timeout is set to 1 and the
banner mode is set to once after reset (
zc1
). This is done to allow the longest data
packet to be set without breaking over hop boundaries.
The maximum number of bytes that can be sent as a single message in Store and
Forward mode is determined by baud rate and hop time according to the formula;
baud rate X hop time = Maximum packet size in bytes (max=188 bytes)
10
The following table shows examples of baud rate vs. hop time and the resulting
packet length in bytes.
default
115200
38 bytes
57 bytes
86 bytes
115 bytes
144 bytes
172 bytes
max
57600
19 bytes
28 bytes
43 bytes
57 bytes
72 bytes
86 bytes
101 bytes
38400
12 bytes
19 bytes
28 bytes
38 bytes
48 bytes
57 bytes
67 bytes
28800
9 bytes
14 bytes
21 bytes
28 bytes
36 bytes
43 bytes
50 bytes
19200
6 bytes
9 bytes
14 bytes
19 bytes
24 bytes
28 bytes
33 bytes
14400
4 bytes
7 bytes
10 bytes
14 bytes
18 bytes
21 bytes
25 bytes
9600
3 bytes
4 bytes
7 bytes
9 bytes
12 bytes
14 bytes
16 bytes
2400
0 bytes
1 bytes
1 bytes
2 bytes
3 bytes
3 bytes
4 bytes
ba
ud r
a
te
3.3ms 5ms 7.5ms 10ms 12.5ms 15ms 17.7ms
hop time
2.3. Modes of Operation
2.3.1. Control and Data Modes
The WIT2450 has two modes of operation: Control mode and Data mode. When in
Control Mode, the various radio and modem parameters can be modified. When in Data
Mode, only data can be transmitted. The default mode is Data Mode. There are two
ways to enter Control Mode. The first way is to assert the Configure (CFG) pin on the
modem. Upon entering Control Mode, the modem will respond with a
>
prompt. After
each command is entered, the modem will again respond with a
>
prompt. As long as the
CFG pin is asserted, data sent to the modem will be interpreted as command data. Once
the CFG pin is deasserted, the modem will return to Data Mode.
The second method for entering Control Mode is to send the escape sequence
:wit2410
(all lower case) followed by a carriage return. In the default mode, the escape sequence
is only valid immediately after power up or after deassertion of the Sleep pin on the
modem. The modem will respond in the same way with a
>
prompt. To return to Data
Mode, enter the
Exit Modem Control Mode
command,
z>,
or assert and deassert the