Multitech MMH900, User Manual

Page: 143 / 200

143
Appendix F - Flow Control Background
minicomputer so that the mux’s buffer capacity is not exceeded. We
chose Xon/Xoff flow control for this example and are setting pace ON for
all channel devices.
1
2
3
4
5
6
7
8
Mux
Link
Channel
NODE 1
Mini-
Computer
1
2
3
4
5
6
7
8
Channel
Mux
Link
Mux
1
2
3
4
5
6
7
8
PC
PC
PC
PC
PC
PC
PC
Printer
Channel
NODE 1 NODE 2
Mini-
Computer
MiniComputer Flow Control
In the example below, the flow control on the minicomputer works as
follows:
1
2
3
4
5
6
7
8
Mux
Link
Channel
Mini-
Computer
A.
B.
C.
D.
mux process
data to the link
mux buffers
full
mux buffers
empty
mux processes
data to the link
Data
Flow Control
off
Flow Control
on
Data
A. Data volume from the mini for any particular channel is appropriate
for the mux to process and transfer on to the link.
B. Data overwhelms a channel's mux buffer and the mux sends a stop
data Flow Control (OFF) signal to the mini stopping data output.
C. The mux buffer sufficiently enpties to allow additional data transfer,