Accession Number : ADA227181

Title :   The High Speed Buffer Board A SAIL EIA-485 Communications Accelerator Card for the Vector Measuring Current Meter.

Descriptive Note : Technical rept.,

Corporate Author : WOODS HOLE OCEANOGRAPHIC INSTITUTION MA

Personal Author(s) : Singer, Robin ; Butler, Douglas M.

Report Date : JUL 1990

Pagination or Media Count : 52

Abstract : A High Speed Buffer Board )HSBB) has been developed for the Vector Measuring Current Meter(VMCM) to implement the transmission of data at 9600 baud over an EIA-485 link. The HSBB significantly extends the VMCM communication functionality, which was previously limited to 300 baud transmission via 20mA current loop or FSK telemetry. The increased speed allows rapid sampling of a large number of current meters on a common cable and the EIA-485 circuitry, which was designed for low power operation, provides a useful multipoint communication method for data transmission over long cable lengths. SAIL protocol (IEEE 997) was utilized to coordinate data transfer by the instruments on a common link. An MC68HC11 microcontroller resides in the VMCM, buffering data it receives at 300 baud from the VMCM UART. In response to a jumper selectable SAIL address, the MC68HC11 offloads the data 9600 baud via EIA-485 to the SAIL controller. Synchronous data collection from many instruments is ensured by the SAIL synoptic set command and an embedded resynchronization/reset command. The low power consumption allows deployments of six months or more with a standard VMCM battery stack. (rrh)

Descriptors :   *BUFFERS, *DATA TRANSMISSION SYSTEMS, *FLOWMETERS, *SAMPLING, *TELEMETER SYSTEMS, CABLES, COMMUNICATION AND RADIO SYSTEMS, CONTROL, COORDINATES, DEPLOYMENT, ENERGY CONSUMPTION, INFORMATION TRANSFER, LENGTH, LOW POWER, MEASUREMENT, OPERATION, VECTOR ANALYSIS.

Subject Categories : Telemetry

Distribution Statement : APPROVED FOR PUBLIC RELEASE