CHAPTER 3: CONNECTING TO DEVICES AND NETWORKS
D20MX HARDWARE USER'S MANUAL
To provide higher EMC immunity and maintain CE Mark radiated emission compliance, the
serial cables used for permanent serial and D.20 Link connections must comply with the
Cables must be shielded
D-type connector covers must provide EMC shielding (e.g. metallized plastic or die cast
Seven serial communications ports are brought out to the backplane connector P2. These
serial ports are five-signal (TXD, RXD, RTS#, CTS#, DCD#) DTE serial ports, compliant to
ANSI/TIA-232 and TIA/EIA-694 specifications and are hosted by UARTs.
The D20MX is tested with all 7 serial ports running at 19200 baud with 20% CPU utilization.
Refer to application configuration guides for supported baud rates and for data bits.
To avoid burning out the WESTERM or D20MX mainboard when directly connecting a rear-
panel serial port on one D20MX chassis to another rear-panel serial port on any type of
D20 chassis, jumper the WESTERM of both chassis' to not provide a power connection to
pin 4. Refer to the appropriate WESTERM module layout for jumper settings.
Communications between the D20 and the D20 peripheral I/O modules are carried over a
high-speed, high-level data link control (HDLC) protocol called the D.20 Link. The D.20 Link
has the following features:
RS-485 serial link, half duplex, 250 kbps
D.20 frame using HDLC protocol format with Manchester encoding
Supports up to 31 D20 I/O peripheral modules in a standard configuration
Repeater/extension modules (GE part number 520-0148) may be used to extend this
limit to a maximum of 120 peripheral modules. The D20MX is compatible only with
certain peripheral common code (i.e., pcommon) versions as defined in Table 11.
Table 11: PCOMMON versions compatible with the D20MX
P022 - PCOMMON for D20C
P010 - PCOMMON for D20A, D20S and D20K
P087 - pBOOT for D20AC
Versions compatible with the D20MX