B&B Electronics 232MSS2 - Datasheet User Manual
Page 2
232MSS2-0812ds -2/3
© 2003 by B&B Electronics. All rights reserved.
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Timer Features
The 232MSS2 has an enhanced mode, which offers special
timer features. The timer features can be used to prevent slave
devices from receiving preamble commands, inadvertent
switching from binary/graphic file transfers, and inactive slave
devices from holding control of the master port. The timer has
two different modes: an inactivity mode and an inadvertent
switch mode. When in inactivity mode, the 232MSS2 will
monitor the data lines. If there is no activity for the specified
time, the selected slave port will be disconnected from the
master port. When in inadvertent switch mode, the 232MSS2
will ignore switching commands for the specified time. After
this time has expired, the selected slave port will be
disconnected from the master port.
Timer functions are enabled via a dipswitch setting and
through software commands. Software commands follow the
same format as preamble codes used for switching. Two
commands are used to set the timer functions: Set Timer Mode
and Set Timer Value. These commands require an additional
byte for data. The Set Timer Value command requires the third
byte to be an ASCII “T” character. The data byte (fourth byte)
must be a value between ASCII “0” and ASCII “9”. A value of
“0” is used to disable the timer. Refer to Table 3 for timer
values.
The Set Timer Mode command requires the third byte to be an ASCII “M”. If the
data byte (fourth byte) is an ASCII “0” (default), the timer will be setup as an
inactivity timer. When the timer is configured as an inactivity timer, the 232MSS2
will monitor the data lines (TD & RD) for data. If there is no activity for the
specified timer value, the slave port that is connected to the master port will be
disconnected. In smart switch mode, the inactivity timer can be used to prevent
the preamble codes from being received by the slave devices. In port combiner
mode, the inactivity timer can be used to prevent devices from tying up the master
port. For example (port combiner mode): All the slave ports have their handshake
lines asserted. The device on Port C has its handshake line asserted and is
currently connected to the master port, but has not been transmitting or receiving
data. When the inactivity timer expires, Port C will be disconnected and the next
slave port will then be connected to the master port (following the first come-first
serve rule). Port C will then be placed at the “end of the line”.
If the data byte of the Set Timer Mode command is an ASCII “1”, the timer will be
set up to ignore switching commands. When the timer is configured in this mode,
the 232MSS2 will not accept any switching commands (“A”, ”B”, ”C”, ”D”, or
“EOT”) for the specified timer value. After the timer has expired the slave port that
is connected to the master port will be disconnected. This feature is useful to
prevent inadvertent switching during binary/graphic type file transfers. For
example (smart switch mode): the timer is configured to ignore switching
commands for 5 seconds. The select Port D command is sent to the 232MSS2.
Once Port D is connected a file of unknown data type (so file may or may not
contain a switching command sequence) is to be transferred through the
232MSS2. For a period of 5 seconds after Port D is connected, no switching
commands will be accepted. As long as the file transfer takes less than 5
seconds, there is no chance the 232MSS2 will inadvertently switch ports.
Table 1 - Communication & Port Setup
Dipswitch SW1
Setting
1
2
3
4
5
6
7
8
0
0
0
X
X
X
X
X
1200 Baud
1
0
0
X
X
X
X
X
2400 Baud
0
1
0
X
X
X
X
X
4800 Baud
1
1
0
X
X
X
X
X
9600 Baud*
0
0
1
X
X
X
X
X
19.2K Baud
1
0
1
X
X
X
X
X
38.4K Baud
0
1
1
X
X
X
X
X
57.6K Baud
1
1
1
X
X
X
X
X
115.2K Baud
X
X
X
0
X
X
X
X
Enhanced Disabled *
X
X
X
1
X
X
X
X
Enhanced Enable
X
X
X
X
0
X
X
X
8 Data Bits *
X
X
X
X
1
X
X
X
7 Data Bits
X
X
X
X
X
0
X
X
Parity Disabled *
X
X
X
X
X
1
X
X
Parity Enabled
X
X
X
X
X
X
0
X
Smart Switch Mode*
X
X
X
X
X
X
1
X
Port Combiner Mode
X
X
X
X
X
X
X
0
DCE master port *
X
X
X
X
X
X
X
1
DTE master port
0 = OFF 1 = ON X = DON'T CARE
*Factory defaults
Table 2
Programmable Character Setting
Dipswitch SW2*
Weight
1
1
2
2
3
4
4
8
5
16
6
32
7
64
8
128
*Factory Default --
ASCII “STX” character
(decimal 2), SW2 position is only one ON.
Table 3 - Timer Values
Data Byte
Value
0
timer disabled
1
10ms
2
25ms
3
100ms
4
500ms
5
1 s
6
5 s
7
30 s
8
1 min.
9
5 min.