ZyXEL NMS BRIDGE CARD NB-100
( LAN <=> RS232 conversion board )
1. Application
In ZyXEL network management system, there is an optional bridge card used to convert NMS LAN(2.5Mbps) packet frame to RS232 async data. It can be used to connect RACK LAN interbus with PC ( in this case, NB-100 act as a DCE equipment role ) which runs ZyView V2.0 NMS. In the other way, it also can be used to act as a data bridge ( in this case, NB-100 act as a DTE equipment role when connects to modems ) which supports PC management console to monitor the rack modems which installed in the
remote site.
The NB-100 occupies one slot of rack, installed with an adapter which plugs into the corresponding RS232 port, converts the packet frame of LAN to RS232 async N.8.1 formated data and vice versa. The data in the RS232 end can be sent to the remote site by a modem link, a serial port provided by T1 mux, or a X.25 pad ( assume the link has been manually established ).
Basically, the NB-100 card supports two kinds of protocols, one is Bisync the other is UDP/IP+SLIP, when the bridge card connection is using the channels like modem link, T1 mux or X.25 as shown in Fig.1, Bisync protocol is utilized.
Fig.1 Typical bridge card connection diagram ( Bisync protocol )
When NB-100 is cooperated with ZyView V2.4 or later version which support TCP/IP networking capability, in this case, UDP/IP+SLIP is utilized. In Fig.2, we show a connection example for network manager who want to manage the racks which installed in remote site and served as a interconnection role between PSTN and TS (Terminal Server). In Site A, each modem are connected to the port of TS for remote dial in service, in order to manage the racks installed in this site, a port of TS must reserved to connect to NB-100, and assign a remote IP address for NB-100 in TS.
Thus, network manager can configure Site A inside ZyView and manage it without any extra management connection.
Fig.2 Typical bridge card connection diagram ( UDP/IP+SLIP protocol )
2. Installation
The NB-100 are composed by two elements, a conversion card with the same size as U-1496R, and an adapter which is used to split LAN and RS232 signal coming out from the conversion card. The following figure shows the appearance.
Fig.3 NB-100 bridge card
There are 5 LED indicators on the face plate, from top down, PWR, TXD(DTE), RXD(DTE), DTE, DCE, respectively. When we plug the card into slot, the PWR will flash 2 times per second that indicate the card is work well in the first beginning. The TXD and RXD flash only when there is data passing through the RS232 interface. The last two LEDs, DTE and DCE, indicate the role that RS232 plays.
Basically, the RS232 async data is fixed at N.8.1 format( no parity.8 data bits. 1 stop bits), but the bit rate of the data is ajustable by SW2 which shown in Fig.4. The table below shows the correlation between setting and speed.
Fig.4 Bit rate settings of RS232
Bit7 and bit8 of SW2 is used to turn on the DTE/DCE LED, the really DTE/DCE circuit change is controlled by SW3 and SW4, when SW3 ON (1-8), and SW4 OFF ( 1-8 ) make the card to act as a DCE interface. When SW3 OFF and SW4 ON make the card to be a DTE signal connection.
Bit5 and bit6 of SW2 are used to select different kind of protocol,
Bit5=OFFRTS/CTS Flow Control.
Bit5=ONXON/XOFF Flow Control.
Bit6=OFFBiSync Protocol.
Bit6=ONUDP/IP+SLIP Protocol.
Note: When you choose Bit6=ON (UDP/IP+SLIP), only RTS/CTS flow control can be used.
The last part is adapter. It is build by 2 DB25 connector( 1 male, 1 female ) and 2 RJ11 LAN connector( for daisy chain ).
3. Operation
The signal flow in the LAN end is simply follow the CSMA/CD mechanism, but in the RS232 end, there is a little complicate. When we use RTS/CTS as signal flow control. In spite of the huge difference in speed between LAN(2.5Mb/s) and RS232( at most 76.8k), the RTS signal is forced on in the very beginning. When we choose XON/XOFF as signal flow control, loop back RTS(4) to CTS(5) and DTR(20) to DCD(8) in local end.
When the conversion board detect the DCD on, the PWR LED will flash quicker than normal, that means in corporate with CTS, it can start convert LAN packet frame into Bisync RS232 data or UDP/IP+SLIP data. In the opposite direction, the conversion board will decode the data received from RXD pin and packs it back to LAN frame.
Fig.5 RS232 signal flow in the case of DTE role
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