Black Box IC026A-R2 Manual De Usuario

↔IEEE 488 INTERFACE CONVERTER

The heart of the interface converter 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 provided 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 wallmount supply. Regulation to the required +5 volts is
provided by U206 [7805].

Decoding of the microprocessor address space is accomplished with a
Programmable Logic Array [U110 (16L8)]. The Memory space allocation is:

$0000-$7FFF

U103

58258

Static RAM

$A000-$A007

U106

9914A

IEEE Controller

$A800-$A807

U105

6551

UART

$B000-$B00F

U104

65B22

VIA

$B800

U201

74HCT244

SW1 (S201)

$B801

U202

74HCT244

SW2 (S202)

$B802

U203

74HCT244

SW3 (S203)

$E000-$FFFF

U102

2764

Programmed EPROM

7. Theory of Operation 

and Board Layout