Beijer Electronics SCOM Protocol EN - Manual (Page 13)

Monitor Addressing
Beijer Electronics, MAEN975 13
4 Monitor Addressing
By default, a Beijer Electronics MT230 Nautic Monitor supports the standard
SCOM addressing scheme, which allows a total count of 16 monitors within a net-
work. The address of a monitor is set with four DIP switches. If a SCOM command
is sent to a monitor, the ADR field must contain either the broadcast address 0xFF,
or the address of the destination device set by the DIP switches. To eliminate this lim-
it, a new addressing scheme is introduced first with Beijer Electronics MT230 Nautic
Monitors.
According to the previous chapter, the width of the ADR field is 1 byte (or 8 bits).
The standard SCOM addressing scheme uses only the lower 4 bits of this field (only
in case of the broadcast address, all bits are used), allowing a maximum of 16 address-
es.
The new addressing scheme, implemented in Beijer Electronics MT230 Nautic
Monitor, uses also the 4 upper bits. To distinguish between the standard and new ad-
dressing scheme, these bits are called “group bits” or simply “group”. Based on this
definition, the following table shows field ADR in more detail:
As shown in the table, a group between 0 and 14 can be specified. Group 15 is not
supported, to avoid address collision with the broadcast address. Thus, together with
the address field, a total count of 15 x 16 = 240 monitors can be connected to one
network.
Monitor grouping is activated only, if the monitor is set up to use the software con-
figured address, instead of the hardware address specified by the DIP switches. If the
monitor uses the hardware address, the group address is automatically set to 0, re-
gardless of the group configuration.
Beijer Electronics MT230 Nautic Monitor addresses are always given in a dotted no-
tation as “group.address”. This means, if a monitor belongs to group 7 and its address
is 3, the resulting address will be 7.3, which is 115 (0x73). In the standard mode (i.e.
DIP switch address is used), the monitor address will be 0.3 (or simply 3) for the giv-
en example, because the group bits are set to 0.
If a Beijer Electronics MT230 Nautic Monitor is configured as remote controller, it
addresses always monitors within its own group. By definition, a Beijer Electronics
MT230 Nautic Monitor cannot remote control monitors in another group.
Related information
Message Format and Description
ADR bits 7...4 ADR bits 3...0
Group
(0 … 14) Address
(0 … 15)