Motorola MVME162, User Manual

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Serial Interconnections
A-6 User’s Manual
A
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 (e.g., 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
MVME162 are listed in Tables A-5 and A-6.
23 DTR_B Data Terminal Ready (B). Output from DTE to DCE indicating that the
DTE is ready to send or receive data.
24 TxCO_A Transmit Signal Element Timing—DTE (A). Control signal that clocks
output data.
25 TM_A Test Mode (A). Indicates whether the local DCE is under test. In DTE
configuration, ignored. In DCE configuration, always tied inactive and
driven false.
Table A-4. Serial Port B EIA-530 Interconnect Signals (Continued)
Pin
Number
Signal
Mnemonic
Signal Name and Description