Dantel 44210 Installation & Operation Manual page 4

CIRCUIT DESCRIPTION
sal Asynchronous Receiver/Transmitter), TTL and RS-232
receivers/drivers, RS-422 and RS-485 receivers/drivers, MPI
inputs, off-hook and TTL outputs, ring detect/line seize circuit,
transformer, timer, eight-lever DIP switch, and regulated power
supply.
Microprocessor
The microprocessor provides central processing power to coordi-
nate virtually all on-board functions carried out by the 44210.
When power is initially applied to the 44210, a watchdog IC
resets the microprocessor and UART. The microprocessor must
pulse the watch dog IC within 1.2 seconds, or the watchdog IC
resets the microprocessor again. The microprocessor is also reset
manually using a front panel RESET button.
128-byte EEPROM
The 128-byte EEPROM provides non-volatile memory for storing
user specified data, such as telephone numbers and passwords.
The contents of the EEPROM may be changed by the user.
8K-byte EPROM
The 8K-byte EPROM provides non-volatile memory for the
microprocessor programming.
Address Latch and Decoder
The address latch and decoder reads the address switch setting
and programs the microprocessor to recognize that address. The
latch holds (latchs) the port while data is being transmitted and
received.
UART
The UART provides control of all data input/output to and from
the microprocessor and the TTL, RS-232, RS-422, and RS-485
buses. The operation of the UART is initialized by the micropro-
cessor after startup.
TTL and RS-232 Receivers/Drivers
The TTL and RS-232 interfaces have two data lines: a TXD
(transmit data) receiver and an RXD (receive data) driver. There
also are four handshaking and/or control lines: RTS (Request To
Send) and DTR (Data Terminal Ready) receivers and CD (Car-
rier Detect) and MPO (Multi-Purpose Output) drivers. Strapping
points for termination of the differential receivers are located on
the circuit board and must be placed in the TERM position for
the interface being used. For interfaces not being used, the
termination straps must be in the OFF position. Front panel
LEDs are provided on the module to indicate RVD, TXD, CD,
and DTR activity.
P 4 44210/49210-0798 <90-00025>
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