F. Tandem T-Pause and Wang Flow Control Methods
154001UA
F-1
FFFFF..... TTTTTandem T
andem T
andem T
andem T
andem T-Pause and W
-Pause and W
-Pause and W
-Pause and W
-Pause and Wang Flow Control
ang Flow Control
ang Flow Control
ang Flow Control
ang Flow Control
Methods
Methods
Methods
Methods
Methods
Tandem T-Pause Flow Control .......................................................................................................... F-1
Wang Flow Control ............................................................................................................................. F-2
TANDEM T
TANDEM T
TANDEM T
TANDEM T
TANDEM T-PAUSE
-PAUSE
-PAUSE
-PAUSE
-PAUSE
FLOW CONTROL
FLOW CONTROL
FLOW CONTROL
FLOW CONTROL
FLOW CONTROL
T-Pause is a flow control method used in some Tandem minicomputer environ-
ments, basically a form of out-of-band flow control. A typical application is
depicted in Figure F-1. On the terminal end, the device signals to the multiplexer
that it is unable to receive more data by dropping DTR. The 3028 Turbo (CTS 2031
Turbo)
multiplexer at the terminal end is thus set to a Reverse Flow Control (RFC)
option of DTR-/DTR+; no special crossover or tandem option is required.
At the host end, the Tandem computer looks for a rising Pin 12 to signal T-Pause
(XOFF), and a falling Pin 12 to mean Ready (XON). At this end there is a need for
both a special Tandem crossover cable and a Tandem option for the Flow Control
(FC) parameter to do the following:
Invert the DTR signal propagated from the far end, since the
remote's falling DTR must be converted to the host's Rising Pin
12, and
Output the far end's DTR input signal (inverted) on BOTH output
pins 5 and 6. This is done to accommodate existing T-Pause
cabling for various manufacturers. Customers without crossovers
may select either option in customer-supplied crossover.
Note that EIA propagation should be enabled at both ends for the Tandem option
to work properly.
Figure F-1. Tandem T-Pause Flow Control Example
Pin
Pin
Pin
Tandem or
Non-Tandem
Peripheral
Tandem
CPU
®
20
12
6
5
or
Special
Cable
RFC: DTR-/DTR+
EIA PROP: YES
FC: TANDEM
EIA PROP:YES
2031F-1
3028
3028