Dynex DSX - Serial Communication with the Controller

Serial Communication with the Controller
6-16 DSX™ System Service Manual
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6.3.4.3. Pressure Sensing
The SDX-A family of sensors produces a voltage directly proportional to the pressure
applied. This voltage for a 12 volt supply is +/- 11mv full scale span. This equates to +/- 1
psi. An AD 620 instrumentation amplifier is used for the first stage of amplification. This
is followed by an op-amp with a gain that can be adjusted from 1 to 50 in 512 steps, by use
of a Digital potentiometer. At zero voltage there may be an offset of +/- 0.3 mV, there may
also be an offset of +/- 0.5mV due to temperature fluctuations. These are removed by the
use of a second digital potentiometer. The amplified signal is level shifted by 2.5 volts to
ensure that negative pressures can be measured.
6.3.4.4. Voltage Generation and Regulation
The Vcc is for the Control and driver board utilize a Newport Power NMA 2405S that
provides +/5v for a total of 2 Watts.
The Vcc for the Transition board is derived from a Newport Power NME 2405S which
provides 1 Watt @ +5v.
6.3.4.5. Microcomputer
The Z & Pipette Module hardware employs the Hitachi H8/3337F single-chip
Microcomputer operating at 16 MHz. This microcomputer provides 60Kbytes of Flash
ROM and 2Kbytes of RAM. The H8/3337F has the following internal peripheral
capabilities:
9 ports, providing 58 I/O and 8 Input lines
Two 8-bit timers (TMR0, TMR1)
One 16-bit free-running counter (FRC)
Two digital to analog channels (DA0, DA1), with 8-bit resolution
Eight analog to digital channels (AN0 through AN7), with 10-bit resolution
Two serial communications channels (COM0, COM1)
Two pulse width modulation channels (PWM0, PWM1)
6.4 Serial Communication with the Controller
Commands and test data are transferred between the H8 and the external PC controller via a
serial RS-232 interface. Interface drivers and receivers are used between the COM1 serial
communications channel on the H8 and the interface connector to provide proper RS-232
signal levels to the controller. DTR is signalled via Port 8-7