MagTek MCP - Manual (Page 39)

Section 4. Protocol
33
SCENARIOS
This section describes different scenarios to illustrate how the protocol works in various
situations. The scenarios include not only how to exchange various frames but also illustrates
how a node performs error detection and error recovery. Each scenario is provided with a short
description and a list of the protocol rules (defined above) that apply to the situation.
Scenario Notations
The scenarios described below use the following notations:
ÆÆÆ
successfully received frame
Legend:
ÆÆÆ
successfully received frame
ÆXÆ
lost frame (frame sent but not received)
ÆEÆ
frame received with correct header EDC and EDC error in the data field
(bwt)
block wait timeout expiration
Service Requests
Successful Service Request Transaction
S (echo req)
ÆÆÆ
(Rule 1.1)
ÅÅÅ S (echo rsp)
(Rule 1.2)
Service Request Error Handling – request frame lost
S (echo req) ÆXÆ (Rule 1.1)
(bwt)
S (echo req)
ÆÆÆ
(Rule 1.4a)
ÅÅÅ S (echo rsp)
(Rule 1.2)
Service Request Error Handling – response frame lost
S (echo req) ÆÆÆ (Rule 1.1)
ÅXÅ S (echo rsp) (Rule 1.2)
(bwt)
S (echo req)
ÆÆÆ
(Rule 1.4a)
ÅÅÅ S (echo rsp)
(Rule 1.2)