GE Dash 3000 Service Manual page 241

Peripheral Expansion Interface
DAS Communication
Optional Unity Network Communication
Revision A
Assembly Drawings: Theory Of Operation
A 20-pin peripheral expansion interface is provided to support future
use. An active low peripheral present signal may be polled by software to
identify when a peripheral is attached to the monitor. Asynchronous,
AUX, and a switched Ethernet serial communication channels are
supported as well as switched +9-18 V and +5 V power.
The microprocessor communicates with the DAS processor using the
second serial communication controller (SCC) of the communication
processor module (CPM). This asynchronous communication channel
operates at TTL levels and is optically isolated within the DAS.
The microprocessor provides an Ethernet controller, which is
implemented on SCC1 in order to benefit from the additional buffer
descriptors compared to SCC2. Ethernet packets are stored in SRAM
buffers and are transmitted and received by the 10BASE-T transceiver.
The Ethernet clocks are generated from a 20 MHz crystal oscillator
circuit and the transceiver. The transceiver also provides a visual
indication in the form of four LEDS to identify packet transmit, receive,
collision, and link integrity. The status of received data is indicated by
the link integrity signal, which is used by the microprocessor to
determine if the monitor is connected to the Unity Network.
An isolation transformer provides basic insulation to the twisted pair
interface required to meet the ANSI/IEEE 802.3 standard (Ethernet).
Isolation is required because during transport the power cord with the
ground conductor is not available to provide a path for a fault condition.
An 8-pin RJ-45 connector containing two isolated, differential pairs is
provided to connect the monitor to a network hub.
NOTE
Power is not provided in the twisted pair interface as in the
attachment user interface (AUI) of other monitoring products.
Dash 3000/4000 Patient Monitor
2000966-339
9-17