Welch Allyn Duet CO2 Module - User Manual - Manual (Page 27)

Duet CO
2
Module OEM Implementation Manual
Welch Allyn OEM Technologies Confidential Page 27
Host/Module Communications
Introduction
The Duet CO
2
Module is a command driven slave device capable of communicating with a host system
over an asynchronous serial communication line. After start up, the Duet CO
2
Module communicates
periodic CO
2
waveform and breath data packets to the host system. All other communication is initiated
by the host system to the Duet CO
2
Module.
The Duet CO
2
Module and the host system are referred to as the “module” and host” in this chapter.
Communication Interface
§ 9600 baud rate (user-selectable)
§ full duplex
§ Asynchronous using standard non return to zero (NRZ) format.
{1 start bit 7 or 8 data bits even parity 1 stop bit}
§ Receive data input (RxD) is the buffered input of a 74HC14. A pull-up is provided on the
module so it can be driven by an open collector source.
§ Transmit data output (TxD) is the collector of a 2N4401 transistor driven with a 10 K base
resistor from the output of a 74HC14. A weak pull-up is provided to source a CMOS load.
§ Non-isolated module power and communications are provided at P104.
System EEPROM
System EEPROM contains system configuration and operational constants that are encoded by Welch
Allyn OEM Technologies. While the majority of parameters pertain to Welch Allyn OEM Technologies
manufacturing and operational defaults, specific parameters may be customized to accommodate
OEM requirements.
System parameters that the OEM may specify a default value include
§ baud rate § module start up mode
§ data format § initial pump flow rate
The baud rate may be set to a maximum of 9600. (Defaults to 9600.)