peterk@cbmger.UUCP (Peter Kittel GERMANY) (11/14/90)
Posting for a friend:
He has an A1000 and wants to operate a modem also with incoming
calls. In the Tech Ref Man there is no RI pin listed for the A1000
serial interface as opposed to all newer models. Is this an error
in the book? Or is there a different way to make it work? (My
friend wants to use a bought software, so it's not so easy to
patch it for some other interface line.) Help available?
--
Best regards, Dr. Peter Kittel // E-Mail to \\ Only my personal opinions...
Commodore Frankfurt, Germany \X/ {uunet|pyramid|rutgers}!cbmvax!cbmger!peterkthad@cup.portal.com (Thad P Floryan) (11/16/90)
peterk@cbmger.UUCP (Peter Kittel GERMANY) in <575@cbmger.UUCP> writes:
He has an A1000 and wants to operate a modem also with incoming
calls. In the Tech Ref Man there is no RI pin listed for the A1000
serial interface as opposed to all newer models. Is this an error
in the book? Or is there a different way to make it work? (My
friend wants to use a bought software, so it's not so easy to
patch it for some other interface line.) Help available?
Nope, no error; the A1000 doesn't respond to the RI on pin 22, though I don't
understand why he (your friend) feels he needs that signal. I produce, among
other things, a special "box" which is purchased mostly by the phone companies
and US Gov't agencies, and I just pass that signal through "just in case"
anyone needs it (no-one does, except those who use DEC-20 computers which are
"ring started" (i.e. their RS-232 connections appear "dead" until the RI
appears); and so I still operate three DEC-20 systems "for reference").
The only two signals (besides RxD and TxD, natch!) to watch are the DSR on
pin 6 and the DCD on pin 8. DSR will be asserted "true" when the modem is
ready to accept a call, and DSD will be asserted "true" when the modem has
established communication with a "remote" modem; then your software can, if
it chooses, look for a "CONNECT 2400" or whatever appearing on pin 3.
Because the subject of RS-232-C seems to be of interest occasionally, I've
included below some material that I posted to another newsgroup regarding
RS-232 pinnings and the meaning of pin 1 and pin 7 concerning grounding.
Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com!thad ]
==================== begin included material ====================
The documentation presented below is a flattened-from-WordPerfect copy of the
material from one of the Appendices of a manual describing one of my hardware
products for which I did all the hardware and software design and PC layout; it
looks much better typeset and printed on a laser printer, and I hope all the
control characters have been removed. And, yes, I also wrote the manual and
it's copyright 1987, but I feel the material (below) will benefit those of you
who are reading this now.
Regarding that product: it is a datacomm product consisting of a complete
microprocessor-based system of which some 50-100 are sold each month (and
have been since 1983); I have substituted "XXXXXXX" for the product's name
since this is not meant as an advertisement. Some of the RS-232-C specs are
derived directly from AT&T and CCITT documents and, surprising to me, most
of the product's customers ARE phone companies (hey, I'm the VP Engineering,
not one of the marketing people :-) Incidentally, I designed that product
to be RFI-clean per the material in "Digital Design for Interference Speci-
fication" (a book by the Keenan Corp.) and the plastic (Pac-Tec) case did NOT
have to be internally painted with NiCr or otherwise shielded to pass FCC and
VDE specs; just another example of doing things "right" from the beginning.
As an aside, the product carries a 5-year warranty, and, to date, the only
warranty repairs have been defective batteries for the static RAMs and a
few defective CMOS chips mfd by a company which shall remain nameless.
In any event, I hope the following serves as a definitive reference for
RS-232-C signals when you're in doubt as to the meaning of some of the common
pinnings. Please note that I have NOT used the word "shield" and that RS-232
pin 1 is clearly described as being a PROTECTIVE GROUND; see the descriptions
for pin 1 (protective) and pin 7 (signal) grounds.
Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com ]
-------------------- begin included material --------------------
RS-232-C SIGNALS
NOMENCLATURE
DCE - Data Communication Equipment, typically a modem; also XXXXXXX's
HOST port which emulates a modem.
DTE - Data Terminal Equipment, typically a host computer or CRT terminal;
also XXXXXXX's MODEM port which emulates a host computer.
SIGNAL STATES
Transmitted and Received Data signals are considered in the marking state
when the voltage on the circuit is more negative than minus three volts with
respect to signal ground, and in the spacing condition when the voltage is more
positive than plus three volts with respect to signal ground. All control and
timing functions are considered ON when the voltage on the circuit is more
positive than plus three volts with respect to signal ground, and are
considered OFF when the voltage on the circuit is more negative than minus
three volts with respect to signal ground. The Data Terminal Ready [DTR](CD)
circuit is "fail-safe" in that a power off condition in the terminal equipment
or a disconnection of the interface cable is interpreted as an OFF condition.
The data, timing and control functions are defined below:
Voltage: NEGATIVE (-) POSITIVE (+)
Binary state: "1" "0"
Signal condition: MARK SPACE
Control and timing function: OFF ON
TERMINATOR IMPEDANCE
The terminating impedance at the receiving end of interface circuits has a
resistive component of not less than 3000 ohms nor greater than 7000 ohms over
the range of voltages for which the signal is defined.
RISE AND FALL TIMES
For control circuits, the time required for a signal to pass through the
transition region of minus three to plus three volts during a change of state
does not exceed one millisecond.
For Received Data [RD](BB), the time required for the signal to pass
through the transition region is greater than one microsecond but does not
exceed 20 microseconds.
OPEN CIRCUIT VOLTAGES
Open circuit driver voltage on any circuit does not exceed +/- 18 volts
with respect to signal ground. When the terminating impedance is between 3000
and 7000 ohms, and the terminator open circuit voltage is zero, the potential
at the point of interface is not less than +/- 5 volts or greater than +/- 15
volts. The terminator on an interface circuit is designed to withstand any
input signal within the +/- 25 volt limit.
Pin Name, Abbreviation, EIA Circuit, CCITT Circuit
1 PROTECTIVE GROUND, FG, AA, 101
A protective (frame) ground circuit is provided by means of the ground wire
on the power cord. This also provides grounding of the chassis. The Signal
Ground circuit (pin 7) is the common reference point for all circuits on the
interface. The Signal Ground and protective grounds are tied together
internally. This arrangement is intended to provide additional margin against
longitudinal power line noise.
2 TRANSMITTED DATA, TxD, BA, 103
Signals on this circuit are generated by DTE and received by DCE. A
positive signal is considered a binary "0" or SPACE and a negative signal is
considered a binary "1" or MARK. The transmitting terminal should hold circuit
[TxD](BA) in the marking state when no data are transmitted, including
intervals between characters.
3 RECEIVED DATA, RxD, BB, 104
Signals on this circuit are generated by a local DCE and received by a DTE
typically in response to signals transmitted by a remote DCE.
4 REQUEST TO SEND, RTS, CA, 105
Signals on this circuit control the data channel transmit function of the
DCE. The ON condition causes the DCE to assume the data channel transmit mode.
The OFF condition causes the DCE to assume the data channel non-transmit mode,
when all data transferred on [TxD](BA) have been transmitted.
5 CLEAR TO SEND, CTS, CB, 106
An ON condition of [CTS](CB) indicates to DTE that a local DCE will
transmit to a remote DCE any data present on the Transmitted Data [TxD](BA)
circuit. If [CTS](CB) is OFF, a local DCE will internally clamp [TxD](BA) to
mark and ignore signals presented on [TxD](BA) by DTE.
[CTS](CB) will be OFF whenever Data Carrier Detected [DCD](CF) is OFF.
6 DATA SET READY, DSR, CC, 107
Signals on this circuit originate from a local DCE to indicate its status.
The ON condition indicates that a DCE is in the data mode and is connected to
the communication channel (telephone line). The ON condition of this circuit
alone should not be interpreted to mean that a communication channel has been
completely established or used to determine the status of any remote DTE.
7 SIGNAL GROUND, SG, AB, 102
This circuit establishes the common ground reference for all interface
circuits. This circuit is normally connected to protective ground (pin 1) to
minimize noise into electronic circuitry.
8 DATA CARRIER DETECTED, DCD, CF, 109 (RECEIVED LINE SIGNAL DETECTED)
The ON condition of this circuit indicates that data carrier is being
received by a local DCE and has been received for at least 155 +/- 50
milliseconds. This circuit will go OFF if the received data carrier falls
below the receiver threshold for more than 17 +/- 7 milliseconds. During the
time that [DCD](CF) is OFF, the received data circuit [RxD](BB) is clamped to
the marking state.
9 ASSERTED POSITIVE (+) VOLTAGE
10 ASSERTED NEGATIVE (-) VOLTAGE
Pin 9 provides +12 volts through a 1KOhm resistor for testing purposes and
for asserting signals at the other circuits of the interface. Pin 10 provides
-12 volts through a 1KOhm resistor for testing purposes and for asserting
signals at the other circuits of the interface. These pins should not be used
by other equipment nor should any extraneous voltages be connected to these
pins.
12 SPEED INDICATION, SI, CI, 122
This circuit will be in the ON state when a local DCE is in the high-speed
mode (e.g. 1200 baud for 212A compatible modems). At all other times this
circuit is in the OFF state. Regarding 212A compatible modems, this circuit's
state does not necessarily correspond with the state of a speed select switch,
particularly with respect to an answering modem which automatically adapts to
the speed of the originating modem each time the data mode is entered (ignoring
its own speed selector).
14 SECONDARY TRANSMIT DATA, STxD, SBA, 118
This circuit is an auxiliary output channel, presently uncommitted, that
will be used by future XXXXXXX options. This circuit is connected only at
XXXXXXX's HOST port.
16 SECONDARY RECEIVE DATA, SRxD, SBB, 119
This circuit is an auxiliary input channel, presently uncommitted, that
will be used by future XXXXXXX options. This circuit is connected only at
XXXXXXX's HOST port.
20 DATA TERMINAL READY, DTR, CD, 108.2
This circuit provides a means for DTE to control the connection of a local
DCE onto the communication channel. The ON condition of this circuit is
necessary to maintain the connection of a DCE to the communication channel.
The ON condition must also be present before a local DCE will enter the data
mode either manually or automatically. If this circuit is turned OFF for more
than 50 milliseconds during a data call, the local DCE will enter an
irreversible disconnect sequence. For automatic answering applications, the
presence of an OFF condition on this circuit does not inhibit the operation of
the Ring Indicator [RI](CE) circuit on pin 22. This circuit must be turned ON
in order for a local DCE to automatically answer an incoming call.
22 RING INDICATOR, RI, CE, 125
The ON condition of this circuit normally indicates that a ringing signal
is being received by a local DCE. The ON condition is approximately
coincident with the ON segment of the ringing cycle. DCEs with answer mode
indication options installed will also maintain the ON condition of this
circuit after the incoming call has been answered and will remain ON as long
as there is an off-hook condition of the telephone line; when the call is
terminated and the telephone line is on-hook, this circuit will turn OFF.
23 SPEED SELECT, SS, CH, 111
This circuit is used on an optional basis to establish the speed mode of a
data call at the originating DCE. When the circuit is implemented, an ON
voltage from DTE will cause the data call to be established in the high speed
mode (e.g. 1200 baud for a 212A compatible modem). An OFF condition will
cause the connection to be established in the low speed mode.
-------------------- end included material --------------------