METRON QA-1290, User & Service Manual, Page: 44 / 65

Voltage Generated from Description
+5 External Supply Regulated 5V in, digital 5V
8.3 Processor System
Refer to Appendix C, Drawing No. E160.20.1000.U1, containing six
schematic diagrams.
The QA-1290 processor board is identical to that used by the QA-90,
except for two modifications. One is that the buzzer on the processor
board is not used and is not fitted. A buzzer on the QA-1290 board is
used instead. The second is that Pin 3 on J60 is strapped to pin 13 on
U1300 instead of +5V. This signals the pulses that step the step mo-
tor.
Refer to Schematic Diagrams 1 through 3 (QA-90; Integrated Key-
board QA-90; and CPU QA-90).
The processor controls the simula-
tions and measurements in the QA-1290. This system is divided into
five function blocks comprising a CPU, memory, display and printer
interface, serial and keypad interface and keypad.
The CPU and keypad board are located behind the front panel. The
unit comprises a processor system, display, control components and a
firmware-controlled SIP port for communication with the QA-1290
board.
The CPU comprises a Motorola 68HC11 operating at 8 MHz, which
gives a BUS frequency of 2 MHz. The UART in µP is used only dur-
ing boot-up. A Maxim µP supervisory circuit with a 4.65 V reset is
used to monitor the 12 V power, and ensure battery power to RAM
when the unit is switched off. U1080 and DS2404 are timer circuits.
These provide the system with real time clock and calendar informa-
tion. U1160 is an address decoder. U1120 is an address latch for the
multiplex address bus. µP has a 64 KB address range, and U1130 to-
gether with U1150 are used as a bank-switch to address the process
circuit’s RAM and Flash-ROM.
Refer to Schematic Diagram 4 (Memory QA-90). The memory com-
ponent comprises 128 KB RAM and either a 28F200 or a 28F400
Flash-ROM for storing programs. The CPU module is programmable
and may be re-programmed with new software supplied by Metron.
Transistors in the memory circuit are used to supply the flash-ROM
with a 12 volt programming voltage.
Refer to Schematic Diagram 5 (Printer and Display IF, QA-90). The
printer and display interface comprises PD71055, PIO that is used to
write to display and to the Centronics output. Data to Centronics goes
via LS05, which has an open collector output. A strobe pulse to the
Centronics port is established through U1410. Keypad scanning and
the RS-232 interface are established by U1300, DUART. The keypad
is a standard keypad matrix. U1310, MAX238 is an RS-232 transmit-
ter/receiver between DUART and the RS-232 port.
8-4