IBM 6580 User Manual

SYSTEM CARD
The system card controls the following
system functions.
•
System Bus
•
Microprocessor and Clock
•
Read Only Storage (ROS)
•
Interrupt Controller
•
Keyboard Adapter
•
Printer Data Link
•
Timer.
The system card is connected to the
distribution board in position B. The
system card has two connectors on the
back of the card for the system bus
extension to the diskette drive (Sl)
and the signal wires for the lower
five light emitting diodes (LEDs) on
panel 1 (S2). These will be covered
later in this section.
System Bus
The cards and function blocks (within
the cards) are connected by the system
bus (Figure 6-3) which carries data
and instructions through the system.
The diskette adapter signal cable is
an extension of the system bus. The
diskette adapter card is in the
diskette unit.
The bus buffers are system bus isolat-
ing devices (switches) used to sepa-
rate the electronics into four
sections (Figure 6-4) during the Basic
Assurance Test (BAT) which occurs with
each power on reset (POR) . The
sections of the electronics are tested
one at a time.
During POR, the microprocessor, the
clock, and Read Only Storage (ROS) are
isolated and tested. Once the correct
operation of this section is deter-
mined, the microprocessor turns on the
bus buffers in sequence. Bus buffer 1
permits the microprocessor to check
the timer, direct memory access (DMA) ,
interrupt controller, printer data
link, and keyboard adapter. Bus buff-
er 2 permits the micoprocessor to
check the memory card and the display
adapter. Bus buffer 3 permits the
microprocessor to test the diskette
adapter to complete the BAT of the
electronics (Figure 6-4).
If a failure is sensed, a pattern will
be displayed on the lower five LEDs
located on the electronics module base
panel 1 or on the display.
Chapter 6. System Electronics/Power Supply 6-3

IBM 6580 Specifications

General

Brand	IBM
Model	6580
Category	Desktop
Language	English