DESCRIPTION AND OPERATION
MODULE CIRCUITRY
2 - 8
I-E96-302B
®
FSK DIGITAL INPUTS (FIELD BUS MODE)
In the field bus mode, all data and communication are FSK
encoded digital signals on a shared bus and require decoding.
The microprocessor can read any input by specifying the bus
address of the device. The signal enters the FSK communica-
tion circuitry through a transmit/receive gate that works with
the multiplexer and communication circuitry.
Figure
shows the digital input circuit with the FSK multi-
plexer and FSK transmit/receive gate. After decoding the digi-
tal input, the FBS module can store that data in memory or
send it directly to the controlling module (MFP/MFC) through
the I/O expander bus interface.
ANALOG INPUTS (POINT-TO-POINT MODE)
All analog inputs are point-to-point. When operating in the
FSK or baseband mode, the FSK baseband digital communica-
tion signal rides on a small portion of the analog input signal.
Each channel has an analog input filter that separates the
communication signal from the process data (analog input)
before the data goes to the analog-to-digital converter (ADC). In
the FSK communication mode, that input also passes through
the FSK communication circuitry for decoding. In the
Figure 2-5. Digital Input Circuit
TP25182A
COMMON
ACOM
15 I/O CHANNELS
INPUT
NUMBER
FSK
MULTIPLEXER
0
1
2
3
4
.
.
.
.
.
.
13
14
GATE
FSK RECEIVE
FSK TRANSMIT
TRANSMIT ENABLE
CHANNEL
SELECT
FROM
MICROPROCESSOR
TO FSK
COMMUNICATION
CIRCUITRY
0
1
2
3
.
.
11
12
13
14
