Fresenius Medical Care 4008 HDF 3/11.97 (TM) 4-41
4.6 LP 763 SSE serial interface extender
4.6.1 Description
● General
The LP 763 is necessary for serial communication of the monitor with the scales and the HDF
pump module.
● Circuit structure
The circuit of the LP 763 comprises two circuit units independent of each other.
Serial interfaces
Heart of the LP 763 P.C.B. is an 8-fold UART (universal asynchronous receiver/transmitter), i.e.
an interface IC (IC 1) with eight independent serial channels. Also to be found on the P.C.B. are
two TTL/RS232 level converters (IC 2 and IC 3) and an interrupt logic IC (IC 4), as well as diverse
resistors, capacitors and an oscillation quartz Q1 for generating the working cycle for IC 1.
COMMCO connection
The slot 63Z used by the LP 763 P.C.B. is also provided for the installation of P.C.B. LP 752. The
LP 752 takes over the connection of the 4008 monitor signals to the COMMCO P.C.B. LP 729. In
order to be able to also continue the linking to COMMCO/FINESSE in 4008 HDF machines the
circuit section of the LP 752 P.C.B. is taken over in the LP 763 P.C.B..
● Function
After switching on the machine the UART is initialled with the transmission parameters.
Transmission parameter channel A:
1200 Baud, 8 databits, 1 stopbit, no paritibit
Transmission parameter channel B:
9600 Baud, 8 databits, 1 stopbit, no paritibit
Channel A is responsible for communication with the scales, channel B for communication with
the HDF pump module.
After going through the watchdog test the scales are switched on through the transmission line
from channel A and the weight requirements of the 4008 monitor are communicated to the scales.
The weight value of the scales is read by the 4008 monitor on the reception line.
Commands and data from the 4008 monitor are sent through the transmission line from channel
B to the HDF pump modules. Data which comes from the HDF pump module is received by the
4008 monitor through the receiving line.
The remaining six communication channels are not used in 4008 operation.
If UART data is ready for collecting or if the transmission buffer is ready to accept new digits
during a transmission the component causes an interrupt at CPU 1. CPU 1 processes this
interrupt demand (in so far as nothing more important is to be done) and reads a digit from the
reception buffer or writes a digit on the transmission buffer.
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