INTRODUCTION
WBPEEUI240754A0
2 - 1
SECTION 2 - DESCRIPTION AND OPERATION
INTRODUCTION
This section explains the output circuitry, control logic, data,
logic power and connections for the IMDSO15 Digital Output
(DSO) module. The DSO is a digital signal interface between a
Multi-Function Processor (MFP) or Logic Master Module (LMM)
and process field devices. The control module communicates with
its I/O module on a I/O expander bus shown in Figure
. Each
I/O module on the bus has a unique address set by its address
dipswitch (S1).
OUTPUTS
The DSO module digital outputs switch voltages up to 120
VAC for AC voltages or 48 VDC for DC voltages. This voltage
energizes (turns on) and de-energizes (turns off) a field device.
MODULE BLOCK DIAGRAM
The DSO consists of registers, buffers and interface circuits.
They control the relay switching and transmit I/O module
operating status back to a control module. Electromechanical
relays provide the switching functions.
is a block diagram of the DSO module. It illustrates
signal flow through the module.
Digital Output Circuits
Each of the eight output circuits consists of a changeover con-
tact of an electromechanical relay. The COM, NC, and NO con-
tacts are available for the field devices on the P3 card edge
connector (Figure
). The on-board relays are driven by two
transistor array integrated circuits which provide an extra
voltage suppressor diode for each channel.
The data selector block drives the output circuits and lights
the front panel output status LEDs. It uses data from the out-
put register or default register to do this. During normal oper-
ation, it selects the output register data.
Output Control Logic
An output register holds the data that controls the outputs.
The I/O expander bus interface writes control module data to
this register. This data, sent to the data selector, determines
the relay states (active or non-active).
