Measurement Computing Serial488/4 - Manual (Page 83)

Section 5 Service Information
5.1
Service Information
5.1 Factory Service
-EASUREMENT
If problems are encountered in using the Serial488/4 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.
5.2 Theory of Operation
The Heart of the Serial488/4 is a 2 Mhz 6809 microprocessor [U 101] supported
by 8K bytes of firmware EPROM [U102 (27128)] and 64k bytes of static RAM [U103
& U104 (58256)]. A Versatile Interface Adapter [U104 (65B22)] is used to generate
real-time interrupts for the firmw are operating system and drive the front panel LED
annunciators through inverters [U112 & U113 (74LS04)].
The IEEE 488 bus interface is accomplished by a TMS9914A [U105] controller
with drivers [U 106 (75160) and U 107(75162)]. T he four serial interfaces use two
Z8530 [U119 & U120] Serial Communications Controllers with four RS232 drivers
[U121, U122, U123, &U124 (LT1081)] , two RS422 drivers [U 126 & U 127
(26LS31)], and two RS422 receivers [U128 & U129 (26LS33)].
Decoding of the microprocessor address space is accomplished with two
Programmable Logic Array [U108 & U 111 (16L8)]. The Memory space allocation
is…
Address Device Part Number Function
$0000-$7FFF U103 58256 Static RAM
$8000-$E6FF U104 58256 Static RAM
$E700-$E70F U106 TMS9914A IEEE Controller
$E710-$E71F U114 74HCT240 SW1
$E760-$E76F U120 Z8530 Serial Controller
$E770-$E77F U119 Z8530 Serial Controller
$E780-$E7FF U110 R65C22 VIA
$E800-$FFFF U102 27128 Programmed EPROM