RAD Data comm ASM-20 operation manual IR-X.21B Interface Module, Position

ASM-20Installation and Operation ManualAppendix C. IR- X.21B Interface Module

	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-3and 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	C V
	IN T/R
	E X T

INT/RCV clock setting

EXT

clock setting

Connector DB -15

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.

EXT Mode C-3