Motorola MVME2700 Series Servisní příručka stáhnout pdf (Strana 192)

B-8 Computer Group Literature Center Web Site

Serial Interconnections

Interface Characteristics

In specifying parameters for serial binary data interchange between DTE

and DCE devices, the EIA-530 standard assumes the use of balanced lines,

except for the Remote Loopback, Local Loopback, and Test Mode lines,

which are single-ended. Balanced-line data interchange is generally

employed in preference to unbalanced-line data interchange where any of

the following conditions prevail:

❏ The interconnection cable is too long for effective unbalanced

operation.

❏ The interconnection cable is exposed to extraneous noise sources

that may cause an unwanted voltage in excess of

1V measured

differentially between the signal conductor and circuit ground at the

load end of the cable, with a 50

Ω

resistor substituted for the

transmitter.

❏ It is necessary to minimize interference with other signals.

❏ Inversion of signals may be required (for example, plus polarity

MARK to minus polarity MARK may be achieved by inverting the

cable pair).

EIA-530 interface transmitter and receiver parameters applicable to the

MVME2700 are listed in the following tables.

Table B-5. EIA-530 Interface Transmitter Characteristics

Parameter Value Unit

Minimum Maximum

Differential output voltage (absolute, with

100

Ω

load)

2.0 V

Open circuit differential voltage output

(absolute)

6.0 V

1 2 ... 187 188 189 190 191 192 193 194 195 196 197 ... 214 215

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Motorola MVME2700 Series Servisní příručka Strana 192