DESCRIPTION AND OPERATION
I-E96-217A
2 - 5
The two ACIA circuits, one for each port, perform:
•
Serial to parallel conversion on data received serially from a
computer.
•
Parallel to serial conversion on data sent to a computer.
•
Byte framing based on the port option switches.
•
Parity, overrun and framing error checks.
•
Peripheral or modem control (i.e., Clear To Send (CTS),
Data Set Ready (DSR) and Data Terminal Ready (DTR)).
Each ACIA has a control register and data transmit/receive
register, each register is selectable by the microprocessor. The
ACIA receives the values set on the port option switch from the
microprocessor. It uses these values to set byte framing and
parity: number of bits (seven or eight), number of stop bits (one
or two) and type of parity (odd, even or none). The data trans-
mit/receive register holds values being transmitted or received
by the SPM. The ACIA automatically removes the start and
stop bits from received data.
A frequency multiplier circuit uses the on-board 1.8432 MHZ
crystal oscillator to develop clock signals required to provide
the jumper selectable baud rates. The SPM can be set to a 300,
1200, 2400, 9600 or 19.2 Kbaud rate using jumper JP9 and
JP10. The selected frequency is sent to the ACIAs: JP9 sets
port 1 rate and JP10 sets port 2 rate.
Refer to
in this section for an
explanation of handshaking and data signals, and connections
for the RS-232C serial ports.
I/O CIRCUIT CONNECTIONS
The two RS-232C serial port interface circuits connect to the
30-pin card edge connector (P3), and XU37 (port 2) and XU38
(port 1). A termination cable routes the I/O signals between P3
of the SPM and a TU. A ribbon cable routes the I/O between
XU37 and the faceplate connector. XU38 is not used.
MODULE BUS
The INFI 90 module bus is a peer-to-peer, serial communica-
tion bus. It provides a communication path between modules
connected to it. An SPM performs the interface functions for a
computer. The P1 card edge connector of the SPM connects to
the module bus.
The module bus is a serial signal line located on the Module
Mounting Unit (MMU) backplane. It provides a communication
connection point for up to 32 separate modules, each with a
unique address (0 to 31).
