Measurement Computing Digital488/80A - Manual (Page 25)

Digital488/80A Power & Assembly 3
Introduction…… 19
Internal Components…… 19
Factory Service…… 19
Power Line & Fuse Configuration…… 20
Line Voltage Selection…… 20
To Select the Line Voltage…… 21
Fuse Replacement…… 22
To Replace the Fuse…… 22
Rack-Mount & Bench-Top Assembly…… 23
Rack Mount…… 23
Bench Top…… 23
Power-Up & Programming Tests…… 24
Power-Up Activation…… 24
Programming Examples……25
KYBDCTRL.BAS Program…… 25
To Run the Keyboard Controller Program…… 25
Digital488/80A Command Responses…… 26
Introduction
Internal Components
The heart of the Digital488/80A is a 6809 microprocessor [U1] supported by 8K bytes of firmware
EPROM [U2] and 32K bytes of battery-backed-up RAM [U3]. Interface to the IEEE 488 bus is
accomplished by a 9914 interface chip [U13]. A 65B22 [U14] generates real-time interrupts for the
firmware operating system and also drives the front panel LED indicators. The digital I/O ports are
controlled through 6821 interface chips [U7, U8, U9, U10, U11, U16]. High-voltage, high-current output
capability is provided on both channels if the HVCX1 option is used. Power is supplied by an on-board
transformer and full-wave rectifier. Regulation to the required +5 volts is provided by an 78T05CT [U15].
The memory space allocation on the Digital488/80A is:
Address Device Part Number Function
$0000-$7FFF U3 84256 32K x 8 RAM
$8010-$8014 U7 68B21 Digital I/O
$8020-$8024 U8 68B21 Digital I/O
$8040-$8044 U9 68B21 Digital I/O
$8080-$8084 U10 68B21 Digital I/O
$8100-$8104 U11 68B21 Digital I/O
$8200-$8204 U16 68B21 Digital I/O
$8800-$8810 U14 65B22 Timer, Digital I/O
$9000-$9907 U13 TMS9914A IEEE 488 Interface
$E000-$FFFF U2 2764 Programmed EPROM
Factory Service
Chapter 7: Troubleshooting provides a troubleshooting reference for possible solutions to technical
problems. Before calling for technical assistance, refer to this chapter.
However, if problems in using the Digital488/80A still persist, you should contact the factory. Many
problems can be resolved by discussing the problems with the appropriate applications department. If the
problem cannot be solved by this method, you will be instructed as to the proper return procedure.
Digital488/80A User’s Manual Digital488/80A Power & Assembly 19