Measurement-computing Serial488A Manuel d'utilisateur télécharger pdf (Page 71)

6.1

Service Information

6.1 Factory Service

f problems are encountered in using the

Serial488A

you should first telephone

the factory. Many problems can be resolved by discussing the problems with our

applications department. If the problem cannot be solved by this method, you will be

instructed as to the proper return procedure.

6.2 Theory of Operation

The Heart of the

Serial488A

is a 6809 microprocessor [U101] supported by 8K

bytes of firmware EPROM [U102 (2764)] and 32K bytes of static RAM [U103

(58256)]. A Versatile Interface Adapter [U104 (65B22)] is used to generate real-time

interrupts for the firmware operating system.

The front panel annunciators are also driven by U104 through an inverter [U113

(74LS04)]. The IEEE 488 bus interface is accomplished by a TMS9914A [U106]

controller with drivers U107 and U108. The serial interface is provide by the UART

[6551 (U105)]. If RS-232 levels are chosen, they are provided by the RS-232

transceiver (U209). If RS-422 levels are selected, the differential driver [26LS30

(U207)] and receiver [26LS33 (U208)] are used.

The internal DIP switches [SW1, SW2 and SW3] are read via 74HCT244 tri-state

buffers [U201, U202 and U203]. Power is supplied by an external unregulated 9 volt

wall mount supply. Regulation to the required +5 volts is provided by U206 [7805].

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Measurement-computing Serial488A Manuel d'utilisateur Page 71