Baldor NextMove BX, Руководство по установке

Страница: 39 / 94

Hardware Features
MN1258V4 08/2000
27
Figure 3-14: 9 Pin Connector
Pin No. Signal Function Type
1 scrn Cable screen/shield Input
2 rxd Receive Data Input
3
txd
Transmit Data Output
4 Not
connected
5
gnd
Signal Ground
6 Not
connected
7 !txd Transmit Data Complement Output
8 !rxd Receive Data Complement Input
9 gnd Signal Ground
See section 4 in the Mint v4 Programmers Manual for details on default software configuration.
3.8.3 RS485 Multi-Drop
NextMove BX supports up to 15 cards using a four wire RS485 serial connection. This
configuration has a
transmit wire pair carrying data from the host to all controllers and a receive wire
pair carrying data from all controllers to the host. Each card is distinguished by a unique address
which is set by software. This address value is stored in EEPROM within the NextMove BX and is
restored at power up. Software details on RS485 multi-drop can be found in the Mint v4
Programmers Manual. A multi-drop layout is shown in Figure 3-15.
Note that the
rxd and txd pairs can be terminated with 120
Ω
resistors. This allows longer cable
lengths for the same data rate as mentioned above. Cable spurs to each controller should be as short
as possible.
The resisters R1 can be fitted as shown to prevent the receive lines picking up noise or cross-talk
from the transmit lines when all controllers have there transmitters disabled.
The RS485 port can also be used in two wire configuration when using one of the data packet
protocols by connecting the pairs (
txd to rxd and !txd to !rxd ). This is possible because the data
packet protocols are half duplex, and only one controller will respond to any packet. In normal
terminal mode the communication is full duplex and two wire connection schemes will not work.