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MODEM.DOC
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1993-05-30
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╥ ╥ ╥─╖ ╥─╖ ╓──╖
║ ║ ╟─╨╖ ╟─╨╖ ╙──╖
╙╜ ╨──╜ ╨──╜ ╙──╜
─────────────────────────────────────────────────────────────
*** VBBS MODEM DOCUMENTATION ***
─────────────────────────────────────────────────────────────
Table of Contents
I. VCONFIG/Channel Configuration
A. COM Port
B. Base Address
C. IRQ
D. Baud Rate
E. Init String
F. Locked Baud Rate
G. Hardware (RTS/CTS) Handshake
H. Minimum Baud Allowed
II. UART Chips and Recommendations
A. Reliability
B. Multitasking
III. Modem Initialization Settings
A. Modem AT Command Settings
B. High Speed Modem Initialization Strings
IV. Discussion of Communications Standards
A. Description of Standards
B. Table of Modes
C. Error Correction Standards
D. Glossary of Terms
V. VBBS FOSSIL Documentation
A. Number of Simultaneous Open Ports
B. 2 Node System
C. 4 Node System
--------------------------------------------------------
VBBS Modem Documentation -- 1
╔════════════════════════════════════════════════════════════════╗
║ I. VCONFIG/Channel Configuration ║
╚════════════════════════════════════════════════════════════════╝
VBBS comes preconfigured to work correctly with most
2400 baud modems. If you are setting up a 2400 baud system,
your modem configuration should be as simple as choosing the
correct modem port in VCONFIG's channel.cfg. High speed
modems will probably require a more complex configuration.
Basic information is provided here for a sampler of those
modems. Due to the variety of systems in use throughout the
network, indepth setup assistance for your specific hardware
is best obtained from the Modem Mania message base,
VirtualNET Sub #209.
VBBS allows multiple phone lines to be configured,
depending on the registration level chosen. For each data
line in VBBS, a channel (phone line) configuration must be
set to define the Serial COM port that the individual line(s)
will be running from. An example follows:
1.) COM Port :
2.) Base Address (Hex):
3.) IRQ (Hex) :
4.) Baud Rate :
5.) Init String :
6.) Locked Baud Rate :
7.) Hardware (RTS/CTS) Handshake :
8.) Minimum Baud allowed :
A. COM Port
═══════════
Define a communications port for each channel in use. COM
ports can be used more than once, but the repeated port must
have a different base address to prevent an IRQ conflict.
B. Base Address
═══════════════
The base address that DOS understands as the port assignment
for the channel. (example: COM1 is 3F8, COM2 is 2F8).
C. IRQ
══════
Assign an IRQ (Interrupt ReQuest) for further definition of
the communications port.
D. Baud Rate
════════════
Define your modem's baud rate speed, from 300 to 57600.
VBBS Modem Documentation -- 2
E. Init String
══════════════
The modem initialization string used by a particular channel
to define reset and operation of the modem.
F. Locked Baud Rate
═══════════════════
Toggle YES/NO for locked baud rate at high speeds. This
should be set to NO for 2400-baud and slower modems.
Note: High-speed modems should use a locked baud rate to
indicate the maximum throughput achieved by the modem. For
instance, a 14400-baud modem could be defined as 14400, 19200,
38400, or 57600, as the modem allows.
G. Hardware (RTS/CTS) Handshake
═══════════════════════════════
Toggle "No, Yes(Normal), or Yes(Slow)". This setting is for
high speed modems. Yes(Normal) is the preferred choice.
H. Minimum Baud Allowed
═══════════════════════
Configure a minimum speed to tailor a high-speed line.
VBBS Modems Documentation -- 3
╔════════════════════════════════════════════════════════════════╗
║ II. UART Chips and Recommendations ║
╚════════════════════════════════════════════════════════════════╝
The NS16550AFN, or UART (Universal Asynchronous
Receiver/Transmitter) chip, is the heart of your asynchronous
communications board. The advantage of the 16550 over the
16450 and 8250 UARTs is that it has a 16 byte buffer.
A. Reliability
On the older chips, with their single-byte buffer,
you would lose data if a second byte came in from the modem
before the CPU had sufficient time to call the first byte.
The 16550, with its 16-byte buffer, gives the CPU up to 16
opportunities to access data before a character is lost.
B. Multitasking
When VBBS is transmitting data, it has to stop the
CPU and fill the UART's transmit buffer. That means that
the background caller will experience a system slowdown while
VBBS attempts to send data to another caller. In addition,
the older 8250 chips were much less reliable, and were never
designed for the high speeds of current modems. The
NS16550AFN, on the other hand, is designed with high bus
speeds and high modem speeds in mind. When multitasking,
even at slower baud rates, the 16550 can be very helpful in
providing smooth operation for the entire system.
VBBS Modems Documentation -- 4
╔════════════════════════════════════════════════════════════════╗
║ III. Modem Initialization Settings ║
╚════════════════════════════════════════════════════════════════╝
Since high speed modems can utilize so many settings,
it is almost impossible to include them all in one initiali-
zation string. Therefore, you may wish to use the NRAM fea-
ture to store the settings which are common to most applica-
tions and use the VBBS init string for VBBS-specific settings.
This collection of modem settings has been garnered
over time from VBBS sysops working with an unlimited variety
of hardware configurations. If the following recommendations
provide unsatisfactory results, please refer to the VirtualNET
support subs for further assistance.
A. Modem AT Command Settings
═════════════════════════════
Standard 2400 bps or 1200 bps Hayes Compatibles (NON-MNP):
Supports the extended "&" command set:
ATX4Q0E0V1&C1&D2S2=251S7=40
X4 Enables extended result codes
Q0 Modem returns result codes
E0 Modem does not echo commands back to the computer
V1 Modem returns verbal result codes
&C1 Modem asserts carrier detect based on connection
status
&D2 On DTR high-to-low transition, modem Hangs Up.
S2=251 Disable modem escape sequence
S7=40 Time modem waits for a carrier when initiating a new
connection
Does not support the extended "&" command set:
ATX4Q0E0V1S2=251S7=40
Modems which do not use the & command set usually have DIP
switches of some type to set their mode of operation. Verify
that your modem is set to assert CD (carrier detect) only
when connected to a remote modem and hang up on drop of DTR
(data terminal ready).
VBBS Modems Documentation -- 5
B. High Speed Modem Initialization Strings
═══════════════════════════════════════════
─────────────────────────────────────────────────────────────
Aceex 14.4
AT&F1S0=0M0E0V1X4&C1&D2&M5\N0S95=1S46=136S36=5
─────────────────────────────────────────────────────────────
Boca 14.4 V32bis:
AT&F E0 V1 Q0 W2 S95=3 S7=50 S0=0
─────────────────────────────────────────────────────────────
Compucom High Speed Modems:
AT&F2*H1%C0\N0S25=2M0QV1ES11=50&C1&D2H&W
Compucom STAR:
AT&F2*H2&D2S7=75&Y0&WX4M0L0S11=50
Recommendations:
A