Paradise P300 specifications DTE Operation, 113 103 105 104 109 102 101 19, 20 RS422 Ground Screen

X.21 DTE OPERATION

This only has a clock to the modem from the terrestrial equipment. Configure a cable with a 15 pin `D` male at one end (X.21 DTE) and either a 25 pin or 37 pin `D` male (not both) at the other end as follows:

Min	X.21 DTE			Signal
	(15 pin D male)
Req				Description
	Name	A	B
DATA CIRCUIT TOWARDS MODEM (TX)

RS422	Circuit	25 pin		37 pin		Electrical
Name	Number					Levels
		A	B	A	B

	S	6	13	Clock In
	R	4	11	Data In
	I	5	12	Sig’ Valid In
DATA CIRCUIT FROM MODEM (RX)
	T	2	9	Data Out
	C	3	10	Sig’ Valid Out
COMMON LINES
	Sig gnd	8		Signal Ground
U	Prot gnd	1		Shield / Prot’
				ground

Clocking: IMPORTANT

TT

SD

RS

RD

RR

SG

PG

113

103

105

104

109

102

101

24	11	17		35
2	14	4		22
4	19	7		25
3	16	6		24
8	10	13		31
7		19, 20, 21
1			1

RS422

RS422

RS422

RS422

RS422

Ground

Screen

The interface will not work as X.21 unless you set the clocking correctly ! The Tx Clocking menu should be set take the single clock from the terrestrial by selecting Tx Clock In. The Rx Clock menu should also be set to return Rx data in time with the single Tx Clock by also selecting Tx Clock In. NO OTHER COMBINATIONS WILL WORK.

The maximum data rate is 10Mbps (over good quality twisted pair screened cable), but this rate is reduced as the connecting cables extend beyond 10m. As an estimate, assume the maximum rate halves as the distance doubles (ie 5Mbps to 20m, 2.5Mbps to 40m etc).

The input clock/data phase is selected automatically, reporting a `Data Marginal` warning whenever it has to switch phase. If the modem reports Data Marginal frequently then this is not a modem fault but an indication that you have a clocking problem external to the modem (ie changing clock/data phase, a problem which would otherwise have caused untraceable data errors). Check the phase of the Data In with respect to the Clock In line.

By selecting Change, Terr-Intfc, Control Lines it is possible to configure the modem to raise an alarm if either the `Sig’ Valid In` line (I) switches to the inactive state. As there is no X.21 equivalent of the RS422 `Device (DTE) Ready In` line (TR), set this to Ignore. It is also possible to configure the Tx carrier to be switched on and off by the `Sig’ Valid In` line (I) by selecting Change, Tx, Modulator, Carrier, RTS-

Controlled.

P300H P300 Series Modem Installation and Operating Handbook Page 174