RFL 9300 RFL Electronics Inc.
October 29, 2001 2 - 4 (973) 334-3100
The RFL 93B SV must first establish its interface with the RFL 93B DISPLAY Display Module in order to obtain
the transmit address for the communications channel. Once this address is obtained the supervisor will pass it
to the RFL 93B CC Communications Controller to trigger the initialization sequence between the two modules.
2.3 COMMUNICATIONS CONTROLLER MODULE
The RFL 93BCC Communications Controller Module controls the formatting, transmission, and reception of all
station-to-station messages. Synchronous serial voice-channel and high-speed digital communications options
are available. The RFL 93B CC Communications Controller Module supports 7.2 KBPS V.29 data over a leased
line and a variety of 56/64 KBPS digital interface modules.
During start-up, the RFL 93B CC "learns" the RFL 9300 's communications configuration by measuring the clock
rate and testing the system control lines. It also checks the system configuration data it receives from the RFL
93B SV module. The RFL 93B CC uses this information to determine its internal software path; there are no
jumpers to set.
The functions that are common to all configurations and speeds are described below, followed by those that are
applicable to more specific applications.
Messages within the 9300 may originate on any controller module. A non-volatile static RAM on the RFL 93B
SV serves as the system "mailbox." All messages between the RFL 93B SV and the RFL 93B CC pass through
this mailbox over an eight-bit bi-directional data bus. When a new message is read, the communications con-
troller first establishes the message's priority and then stores it in its internal RAM. If the message contains time
values, the microcontroller increments the time and discards the message if overflow occurs before the mes-
sage can be sent. The message with the highest priority is compressed and loaded into the transmitter shift reg-
isters, along with CRC bits. The RFL 93B CC module at the remote RFL 9300 uses the CRC bits to test the
validity of the transmitted message.
Simple messages consist of single 15-bit words; eight data bits, six CRC bits, and one framing bit. More compli-
cated messages require two 15-bit words. The transmitter logic circuits supply the framing bit to mark the be-
ginning of each word. The framing bit toggles from word to word. A never-ending stream of messages is con-
tinuously transmitted to insure that the remote terminal can frame regardless of the state of the transmitting ter-
minal. A null word will be transmitted if there is nothing else to send. The RFL 93B CC at the remote RFL 9300
uses a hardware comparator and EPROM lookup table to test the CRC security of each received word. The se-
curity test must be done in hardware because of the high speeds associated with 56-Kbps and 64-Kbps com-
munications. The microcontroller performs the framing function by resetting a 15-state counter when the data,
CRC, and frame bits line up. The counter then automatically generates a latch signal for future data reads by
the microcontroller. Most messages received from the remote RFL 9300 are passed to the RFL 93B SV module
for distribution to other controllers in the system.
2.3.1 SINGLE-CHANNEL MODEM OPERATION
If the first module slot in the RFL 9300 chassis contains a RFL 93B MO Modem Module, the RFL 93B CC initial-
izes and resets the modem through a dedicated 15-bit bus connecting the boards. The RFL 93B MO uses mo-
dem control bits to configure it as a CCITT V.29 modem operating at 7.2 KBPS.
Modems occasionally require training from the remote station. This function is initiated by the RFL 93B CC. The
words passed between the remote or local modems and their respective RFL 93B CC modules are synchro-
nous and serial.
The squelch rules that define a valid word depend on the communications system. These rules apply to each
word as it is received. They determine if an alarm should be issued to the RFL 93B SV Supervisor Controller
Module, or if the serial link between the RFL 93B CC and the modem must be re-framed.
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