Smiths Graseby 3200, Technical & Service Manual

Page: 48 / 117

Smiths Medical International Ltd.
Issue 5 (August 2004)
3200 Service Manual 4 — 5
RS232 interface
WARNING
Only items of equipment that conform to EN60950 may be connected to
the 9-pin RS232 connector that is situated at the rear of the pump. This
conformity prevents the safety of the patient being compromised.
The micro controller generates an RS232 compatible signal with a 0 to 5 V output. IC5,
with ancillary components L5, R33, C18, C19, C20, C21, and C22 converts the 0 to 5 V signal
to a +/-10 V output. IC7 is supplied with a 5 V power rail and uses two charge
pumps to create a 10 V and -10 V supply. R34 A, B, C and D are for electrostatic
protection.
The signals on the D connector are shown on Figure 4.18 , and the pin connections for the
D connector are shown on Table 4.1 .
Table 4.1 RS232 D connector
Pin No. Connection
1 Not connected
2 RxD
3 TxD
4 Not connected
5 GND
6 DSR (handshake out)
7 RTS (+10 V out)
8 CTS (handshake in)
9 Not connected
RS232 serial
interface
Umbilical
connector
The processor communicates with its input and output devices with a serial-in and a serial-out line.
The serial data, MOSI, is converted to a parallel output by three shift registers, IC 8, 9 and 10.
The parallel outputs are used to power the various LEDs and control the keyboard driving
sequence. The keyboard input along with the mains present signal is converted to the serial
signal, MISO, by a parallel input serial output shift register, IC11.
ICs 8 and 9 are linked so that they appear to work as a single 16 bit output serial input shift
register. The signal MOSI is common to IC8 and IC10.
The FPSEL1 and FPSEL2 lines define whether to activate ICs 8 and 9 or ICs 10 and 11.
The SCLK clock signal is fed to all four ICs.
The pump’s front panel input device consists of 11 press-buttons. The ON button when
pressed completes the circuit between pins 1 and 2 on PL3.
The remaining keys use a 3 x 4 matrix. The four lines on PL3 pins 6 to 9 inclusive are pulled
high by resistor R70A, and are connected to IC11. Each line is connected to one of the 4 rows
of the keyboard matrix.
The 3 columns of the matrix, PL3 pins 3 to 5 are connected to IC8, the parallel out serial shift
register. As each individual column is pulled low the status of each key in that column is input
to IC11.
Resistor R66 limits the current in the control lines out of IC8. The diodes D11 to D13 allow IC8
to pull the required control line low but let the remaining lines float when a logic high is applied
at the output of IC8.
Zener diodes D22 to D24 inclusive and quad resistor packs R73 and R74 form the electrostatic
discharge protection circuit.
(contd.)
Input/output
serial interface
The umbilical ribbon cable connector (see Figure 4.9) enables data and the circuit power
supplies to be sent between the main circuit board (front case) and the umbilical board on
the rear case.