LS SERIES SERVICE MANUAL
ISSUE 4.0 MICROPROCESSOR CIRCUITS 1
2. MICROPROCESSOR CIRCUITS
2.1 General
See diagram 04/1455 sheet 4 in section 17
The microprocessor circuits are contained on the Main PCB, which is fitted under the lower
cover. This PCB contains the Microprocessor circuits, Analogue circuits and the USB
interface.
The Full Control Console or the Hand Held Remote is electrically connected to the 37 way D
connector, P5, on the Main PCB and this connector is accessible on the rear of the machine.
The Full Control Console is connected using an external cable, part number 09/0710, but the
Hand Held Remote is supplied with an integral connecting cable.
The loadcell is electrically connected to the 16-way IDC connector, P8, on the Main PCB by
an internal cable that connects to the 15-way D connector on the rear of the machine.
The Motor Drive PCB is electrically connected to the 26-way IDC connector, P7, on the Main
PCB by an internal cable that connects to the 26-way IDC connector, P3, on the Motor Drive
PCB.
The computer is electrically connected to the 4-way Type B USB connector, P14, on the Main
PCB and this connector is accessible on the rear of the machine.
The machine is controlled by a Motorola 68332 microprocessor, IC21, from a software
program held in the 1Mbyte FLASH Memory, IC20. Flash memory is used instead of an
EPROM so that the program may be easily upgraded from a computer. The test parameters
and system variables are held in two 128Kbyte static RAMs, IC19 and IC22 and the test set-
ups and measured data is stored in the battery backed 32Kbyte RAM, IC18.
The microprocessor operates at an internal clock speed of approx. 21MHz that is produced
from a Phase Locked Loop inside the microprocessor using a 32.768KHz crystal, XT1. The
PCB is fitted with a reset switch, S1, which allows a Service Engineer to restart the program
during fault finding.
2.2 USB Interface
See diagram 04/1455 sheet 3 in section 17
The machine can be connected to a computer using a USB cable. The microprocessor
generates RS232 signals using the RS232 interface controller, IC23, which is running from a
3.684MHz crystal oscillator, XT2. These RS232 signals are converted to USB signals via the
FTDI converter, IC37 before being fed to the USB Type B connector.
Note that the FTDI converter is powered from the PC so that the USB connection is always
present when the USB cable is connected to the machine.
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