Motorola MVME167 Series, User Manual

Page: 73 / 84

EIA-232-D Interconnections
A-2 MVME167 Single Board Computer User’s Manual
A
NOTES: 1. A high EIA-232-D signal level is +3 to +15 volts. A low level is -3 to -15 volts.
Connecting units in parallel may produce out-of-range voltages and is contrary
to specifications.
Table A-1. EIA-232-D Interconnections
Pin Number Signal Mnemonic Signal Name and Description
01 Not used.
02 TxD TRANSMIT DATA. Data to be transmitted; input to the modem from the
terminal.
03 RxD RECEIVE DATA. Data which is demodulated from the receive line; output
from the modem to the terminal.
04 RTS REQUEST TO SEND. Input to the modem from the terminal when required
to transmit a message. With RTS off, the modem carrier remains off. When
RTS is turned on, the modem immediately turns on the carrier.
05 CTS CLEAR TO SEND. Output from the modem to the terminal to indicate that
message transmission can begin. When a modem is used, CTS follows the
off-to-on transition of RTS after a time delay.
06 DSR DATA SET READY. Output from the modem to the terminal to indicate that
the modem is ready to transmit data.
07 SIG-GND SIGNAL GROUND. Common return line for all signals at the modem
interface.
08 DCD DATA CARRIER DETECT. Output from the modem to the terminal to
indicate that a valid carrier is being received.
09-14 Not used.
15 TxC TRANSMIT CLOCK (DCE). Output from the modem to the terminal; clocks
data from the terminal to the modem.
16 Not used.
17 RxC RECEIVE CLOCK. Output from the modem to the terminal; clocks data
from the modem to the terminal.
18, 19 Not used.
20 DTR DATA TERMINAL READY. Input to the modem from the terminal;
indicates that the terminal is ready to send or receive data.
21 Not used.
22 RI RING INDICATOR. Output from the modem to the terminal; indicates to the
terminal that an incoming call is present. The terminal causes the modem to
answer the phone by carrying DTR true while RI is active.
23 Not used.
24 TxC TRANSMIT CLOCK (DTE). Input to modem from terminal; same function
as TxC on pin 15.
25 BSY BUSY. Input to modem from terminal. A positive EIA signal applied to this
pin causes the modem to go off-hook and make the associated phone busy.