X25AM Programming Manual

Introduction
X25AM Programming Manual—527201-001
1-5
Assigning Incoming Calls
X25AM supports port numbers from 0 to 9999, except for port numbers contained in
the call user data field. In this case, X25AM supports port numbers from 0 to 99.
Many networks allow a two-digit port number to be appended to the called and calling
addresses. Some networks allow up to four digits, and others do not allow port
numbers at all. When the network does not allow a port number in the called and
calling address fields, X25AM encodes the called port number in the call user data
field.
When a subdevice is added to the configuration, it is assigned a port number that does
not need to be unique. If no port number is specified, it defaults to zero. Your
application can also specify the port number attribute with the SETMODE and
SETPARAM file-system procedures.
Because one X25AM process can have a maximum of 510 subdevices, the maximum
number of ports is 510. Multiple subdevices can be associated with each port number,
as long as the total number of subdevices does not exceed 510.
Assigning Incoming Calls
When X25AM receives a valid incoming call, it begins searching for a free subdevice,
starting with subdevice 1. Subdevice numbers (not port numbers) are allocated
sequentially, starting with 1, in the order that the subdevices are added to the
configuration. The first subdevice is 1, the second is 2, and so on. If some subdevices
are deleted and others added, free numbers are reused in the same order.
Before a call can be assigned to a free subdevice, all of the following must be true:
Figure 1-4. DTE Address, Port Numbers, Subdevices, and Called Address
DTE
#12345678
PORT
#88
PORT
#99
Subdevice D
DTE Address: 12345678
Port Number: 99
Port Number: 88
Called 1234567899
Addreses: 1234567888
VST0104.vsd
Subdevice C
Subdevice B
Subdevice A
Application