ASM-20 Installation and Operation Manual Appendix C. IR- X.21B Interface Module
6/4/99 13:18 EXT Mode C-3
C.4 IR-X.21B Interface Module
The IR-X.21B interface module is shown in Figure C-3. It has two operation
modes which are selectable on the PCB board. The selection is made by
means of the JP2 jumper located within the module as shown in the figure.
The EXT mode is described in EXT Mode on page C-3 and illustrated in
Figure C-4. The INT/RCV mode is described in INT/RCV Mode on page C-4
and illustrated in Figure C-5.
Note The X.21 interface should be in accordance with the modem clock mode. For
example, if the modem is in the EXT mode, then JP2 should be set to the EXT
position.
JP 2
INT/RCV
INT/RCV
clock settin
g
EXT
clock settin
g
Connector DB-15
EXT
Figure C-3 Location of Jumper JP2 in the IR-X.21B Interface Module
C.5 EXT Mode
This mode is used in applications of X.21 networks where the system timing
is provided by the X.21 network. The IR-X.21B module has an internal buffer
to compensate for the phase delay introduced to the system by the line
delay between the two modems. The buffer is a 16-bit FIFO connected as
shown in Figure C-4. When the modem’s clock mode is EXT, the JP2 jumper
must be set to EXT.