Envoy ACP/XF Application Programming Manual

Normal Response Mode (NRM) Protocols
EnvoyACP/XF Application Programming Manual–132179
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Primary or Secondary Station
Although you can set these characteristics during system configuration and can modify
them later by using SCF, you should also use the SETMODE procedure to ensure that
the line characteristics always meet the requirements of the application process.
For additional information on the SETMODE procedure, see SETMODE Procedure
on
page 4-13 A brief description of the line characteristics listed above follows.
Primary or Secondary Station
To activate the data link, the primary or supervisor station issues the SNRM (Set Normal
Response Mode) or the SNRME (Set Normal Response Mode Extended) command to
all secondary stations; to close the link, the primary station issues a DISC (disconnect)
command. Secondary or tributary stations only respond to commands; they never issue
them. Once the link is activated, the primary station can transmit data to any tributary
station. However, tributary stations can transmit data only when the supervisor
specifically permits them to do so (by polling them).
NRM Address Verification
EnvoyACP/XF maintains one station address that you can specify during system
configuration and subsequently alter by using either SCF or a SETMODE 17 procedure.
In a point-to-point environment, the first of these addresses (address #1) is the station
address present in all outgoing frames and expected to be present in all incoming frames.
The second address is not required in a point-to-point NRM environment; you should set
it to 0 using either SCF or a SETMODE procedure. Make sure that both computer
systems are configured compatibly with regard to station addresses.
In a multipoint environment, the primary and all secondaries use station-address lists
created by the DEFINELIST procedure.
SDLC or ADCCP discard any incoming frames that contain a null (all zeros) station
address.
ADCCP-NRM Extended Addressing
You can configure an ADCCP line to use 1-octet, 2-octet, 3-octet, or 4-octet address
fields. When using a basic 1-octet address field, your application process can uniquely
reference up to 254 remote stations. A 2-octet address field increases this number to
65,536, while a 3-octet or 4-octet address field provides a virtually unlimited range of
unique remote station addresses.
During system configuration, you can set the address field size by using the
ADDRESSSIZE modifier. You also can set the address-field size by using the
SETMODE 19 procedure, specifying bits 1 and 2 of parameter2, as follows:
CALL SETMODE (fnum,19,parameter1,parameter2)
parameter2.<1:2> = 0: 1-octet address field
1: 2-octet address field
Note. Use SETMODE 17 only with basic address fields, not with extended address fields.
Note. Extended address fields are not supported by the SDLC protocol.