Dynabyte 5505 User manual

5505
Computer Unit
Technical Manual

1.
2.
3.
4.
5.
6.
7.
GENERAL
Features.
PHYSICAL DESCRIPTION •
Front Panel
Rear Panel
Card
Cage -- S-IOO Bus.
S-IOO Bus Cards •
Power Supply fvt:>dule •
Diskette Drive.
Winchester Drive.
FUNCTIONAL DESCRIPTION •
SPECIFICATIONS •
5505 CCJt1PUTER
MAINTENANCE
TABLE OF CONTENTS
OPERATION AND INSTALLATION •
Unpacking
Ac Line •
Options •
Set Up and Turn On.
MAINTENANCE.
Customer Support Service.
Repacking and Returning Material.
Diagnostics •
Fault Location.
Power Supply fvt:>dule Voltages and Adjustment
Removing Assemblies •
REFERENCES •
S-100
Bus •
.,
Schematics and Replaceable Parts.
OEM EquiJ;ment •
DYNABYTE -Page 1
3
3
6
7
7
.10
.11
.14
.14
.14
.15
.21
.27
.27
.28
.28
.28
.35
.35
.35
.37
.37
.38
.39
.44
.44
.44
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5505 Technical Manual 404512
ILLUSTRATIONS
. ... • 5
Table 1-1 -- 5505 Computer, Models •••
Figure 2-1 -- 5505 Computer, Front Panel . . . . . . . . • 5
Table 2-1 -- 5505 Computer, Front Panel Controls and Indicators. • • • • 6
Figure 2-2 -- 5505 Computer, Rear Panel. • • • • • • • • • • • • 8
Table 2-2 -- 5505 Computer, Rear Panel Controls and Connectors. • 8
Table 2-3 -- 5505 Computer, Interior Major Assemblies •••
Figure 3-1 -- 5505 Computer Functional Block Diagram •
Table 4-1 -- 5505 Computer Functional Specifications • ..
Figure 5-1 -- Central Processing Unit, Option Switch Settings.
Figure 5-2 -- 641< Random Access Memory, Option Switch Settings •
.13
.17
.22
• .31
••• 32
Figure 5-3 -- Disk Controller, Option Switch Settings ••••••
.. .33
.34
.37
Figure 5-4 -- Auxiliary Disk Controller, Option Switch Settings ••
Figure 6-1 -- Dynabyte Identification Plate. • • • • • • • • •
Figure 6-2 -- Power Supply Module Voltage Test Points, BS1 ••••
Table 6-1 -- Troubleshooting Chart • • • • • • •
Table 7-1 -- Dynabyte 8-100 Bus Pin Assignments. • •
Figure 7-1 -- 5505 Computer Chassis Wiring Diagram • •
Table 7-2 --. 5505 Computer Replaceable Parts List.
DYNABYTE -Page 2
..
. . ..
.. •
•• 38
••••• 42
• .45
• .51
.52

5505 Technical Manual
404512
1. GENERAL
1.01 This manual provides a physical and functional description and
the operating theory necessary for effective installation and field service of
the 5505 Computer.
Features
1.02 The 5505 Computer, illustrated on the title page, is supplied indivi-
dually or as a system component to a larger Dynabyte computer system. Its
features include the following:
• Z-80 microprocessor operating at 4 MHz.
• Two serial, software-programmable 110 to 76,800 baud ports. Each of
the ports' data lines may be configured to an RS-232C level or 20 rnA
current loop data communication line interface.
• One parallel port wi th full handshaking logic.
• Double Density Diskette Controller.
• Mini~inchester Controller.
• Built-in Diskette Drive in single-sided or double-sided
configuration (see Table 1-1).
• Built-in Mini~inchester Drive (see Table 1-1).
• Ten internal timers.
• Sixteen priortized vectored interrupts.
• A real-time clock.
• 64K of Random Access Memory. Optional memory to 400K bytes can also
be provided with multiple memory cards.
• The power supply module features pre regulation to minimize
operational problems from brown outs and line voltage surges.
• Efficient cooling of the 5505 S-IOO cards and power supply is assured
by a 4-5/8 inch axial fan furnishing air through the chassis and
exhausted
out through the rear panel.
• The backplane is shielded and fully socketed for 12 S-IOO card
positions.
• Heavy' duty metal construction.
• The front panel switches POWER and RESET-HALT are illuminated.
• A line fuse is provided for ac line protection.
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5505 Technical Manual
404512
• Each internal subassembly is modular and is unit-replaceable for ease
in servicing.
• Each 5505 carries a lBO-day warranty on parts and labor from the date
of shipment from Dynabyte.
• Each 5505 is burned in for a minimum of 72 hours.
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5505 Technical Manual 404512
Table 1-1 -- 5505 ~omputer, Models
5505 -Al 5505 -
Bl
5505 - Cl
Floppy Disk Drive
Surfaces 1 2 2
Unfonnatted Capacity
500K
1000K
1000K
Fonnatted Capacity
315K
655K
655K
Winchester Hard Disk Drive
Surfaces
4 4 6
Unfonnatted Capacity
6. 4MB
10. 67MB
16MB
Formatted Capacity 5. 32MB
a.9MB
13.4MB
1.03 Dynabyte maintains hardware and software compatibility with Dynabyte
S-100 .cards used in the Dynabyte S-IOO Bus only. S-IOO I/O cards, e.g.,
modems, clocks, and parallel ports from other manufacturers will be compatible
with the Dynabyte S-100 Bus in most cases. Contact Dynabyte for specific
applications.
4
Figure 2-1 -- 5505' Computer, Front Panel 807129
DYNABYTE -Page 5

5505 Technical Manual 404512
Key
1
2
3
4
Table 2-1 -- 5505 Computer, Front Panel Controls and Indicators
Element
POWER ON OFF
SWitch and Indicator
RESET Switch and
HALT Indicator
Diskette Drive
Diskette Drive
Select Indicator
Function
Applies the ac line to the 5505 Computer and
the ac power receptacle on the rear panel.
Refer to Figure 2-2, Key 3. The indicator
lights When +8 Vdc is available from the power
supply.
Momentarily grounds the S-IOO Reset line
generating a Power On Clear (POC) sequence:
(1)
CPU Program Counter is reset,
(2) Disk Contoller is reset.
When the indicator is lit, the CPU has stopped
at a Z-80 HLT (76H) instruction in the
program.
Provides for reading and writing onto 5.25"
double and single sided floppy Diskettes for
permanent storage of programs and data files.
Lit when Disk Controller selects drive for a
read
or write operation.
2. PHYSICAL DESCRIPTION
2.01 The 5505 Computer is an integrated piece
incorporating all necessary component assemblies.
are:
(1) Power Supply Module
(2)
Central Processing Unit
(CPU)
(3)
S-lOO Bus Card Cage and Motherboard
(4)
Random Access Memory (RAM)
(5) Floppy Disk
Controller
(6 )
Diskette Drive
(7) Hard Disk
Controller
(8) Winchester Hard Disk Drive
Some of the optional assemblies are:
(9) Octaport (an eight-port seria~ I/O).
(10) Additional Random Access Memory (RAM).
DYNABYTE -Page 6
of electronic equipment
The principle assemblies

5505 Technical Manual 404512
Details on these individual assemblies, as well as their schematic diagrams
and
,replaceable parts lists, are funished under separate cover as individual
technical manuals. These assemblies have been enclosed in an exceptionally
compact package measuring 52 em x 47 em x 18 em (20.5 in. x 18.5 in. x 7 in.)
weighing 25 kg (about 55 lbs.).
2.02 The 5505 draws nominally 400 VA of 115 Vac, 60 Hz commercial power. It
may be factory optioned for operation from a 230 Vac, 50 Hz line.
2.03 The 5505 is designed to operate efficiently in an environment with an
ambient
temperature range from 10 to 35 degrees Centrigrade (50 to 95
degrees Farenheit) and with a relative humidity from 20 to 80 percent.
2.04 Figures 2-1 and 2-2 provide number key callouts of all components
located on the front, rear and interior of the 5505. Associated Tables 2-1
through 2-3 provide a cross reference for each callout, identifying the
respective part as to function, description and/or designation.
Front Panel
2.05 Refer to Figure 2-1 for the description Which follows. The 5505
Computer Front Panel has only two operating controls with which the user
should be concerned.
(1) The POWER ON OFF Switch turns the computer on and off. The switch also
connects the ac line power to a convenience receptacle on the rear panel.
The switch also contains an indicator which lights when there is an output
from the internal +8 Vdc power supply.
(2) The RESET Switch is used to restart the computer if it should become
locked up due to a software or hardware malfunction. Operating the RESET
Switch causes the S-IOO Reset Line, Pin 75, to be active low. The Reset
Line is an input to the Power On Clear (POC) circuits and resets the CPU
Program Counter, Disk Controller, etc. Then the CPU initiates a reboot by
jumping
to a starting address appropriate for the user's system. The switch
also contains an indicator, which, when lit, indicates the CPU has read a
Halt (HLT) instruction and has stopped.
The right half of the front panel contains the 5.25 inch diskette storage
unit.
Rear Panel
2.06 Figure 2-2 illustrates the Rear Panel of the 5505 Computer. Table 2-2
tabulates and describes each of the rear panel elements. Ac line and computer
Input Output (I/O) connections are through the rear panel. At the right, the
ac line is connected through an IEC connector. This permits the 5505 to be
connected domestically to 115 Vac, 60 Hz with a National Electrical
Manufacturers Association (NEMA) cord set or internationally with a cord set
appropriate for that country. A line fuse provides protection for the 5505 and
equipment powered from
the ac convenience receptacle above.
. DYNABYTE -Page 7

5505 Technical Manual 404512
Key
1
2
3
Figure 2-2 -- 5505 Computer, Rear Panel -802470
Table 2-2 -- 5505 Computer
Rear Panel
Controls and Connectors
Element
Function
Ac Line Receptacle
(J6)
lEe standard three-wire male receptacle.
Provides for ac line, neutral and a third
wire bonded to the chassis frame. Mates with
Belden P-2392 ac cord set for U.S. domestic
use
or the appropriate cord set for the export
country.
Ac Line Fuse (Fl)
Provides ac line overcurrent protection:
(1 ) 115
Vac -- 6 A.
(2) 230 Vac -- 3 A.
Early serial number units are provided with a
circuit breaker in this position.
SWITCHED AC OUTLET
N~ three-wire female receptacle provides for
Receptacle
(J7) .
the ac line, neutral and third wire bonded to
the chassis frame. '!his receptacle is switched
DYNABYTE -Page 8

5505 Technical Manual 404Sl2
4
5
6
7
8
9
10
11
Axial Fan
Dynabyte Identification
Plate
SERIAL 1 PRINTER
Port Receptacle
SERIAL 2 TERMINAL
Port Receptacle
PARALLEL I/O Port
Receptacle
FLOPPY DISK I/O
Receptacle
Hard Disk I/O Access
Hole and
Clamp
I/O Port Connector Area
by
the POWER ON Switch on the front panel -
refer to Figure 2-1, Key 1 - and is protected
by fuse, Key 2, above.
Provides for drawing heat from the power
supply module and internal heat dissipating pc
assemblies.
Furnishes the model and serial number neces-
sary for warranty service. Refer to Figure
6-1.
O8-2S-S connector. Optionally EIA RS-232C or
20 rnA current interface. Connection point for
the EIA cable to the Serial Printer.
D8-2S-S connector. Optionally EIA RS-232C or
20 rnA current interface. Connection point for
the EIA cable to the Video Tenninal.
DB-2S-S connector. Eight-bit parallel I/O
connection point to 2S-conductor cable to a
parallel printer.
SO-conductor ribbon connector. Provides a
connection point for the cable to the
Dynabyte 5010 Dual Diskette Storage.
Furnishes a hole and clamp for the cable to
the Dynabyte S012 Cartridge Module Drive or
SOlI or 5013 Winchester Drive.
Provides positions for O8-2S-S connectors.
Figure 2-2 illustrates connectors for:
(1) Three ports from the CPU
(2) Up to 16 ports from;~p to two
Octaport cards. '<
CAUTION
Power consumption from the ac convenience"
receptacle is limited to 200 V A.
2.07 A four-inch fan draws heat dissipated internally out of the rear
panel. Air is drawn into the 5S05 cabinet through louvers provided in the
bottom of the cabinet.
DYNABYTE -Page 9

5505 Technical Manual
IMPORTANT
Install the 5505 Computer so as not to obstruct the air
flow through the louvers in the bottom of the cabinet and
allow a three-inch clearance from the rear of the fan.
404512
Desk-type system
cabinets supplied from Dynabyte are designed to assure
constant air flow through the computer.
2.08 Several mass storage devices can be used with the 5505. The rear panel
furnishes connector access for these devices.
(1) A fifty-pin ribbon cable connector provides for disk I/O signals,
control signals and status signals to a Dynabyte 5010 Dual Diskette Storage
Unit.
(2)
disk
unit.
A rectangular hole provides access for a multi-wire ribbon cable for
I/O signals, control and status to a Dynabyte 5011 or 5013 storage
2.09 Sixteen positions are provided on the rear panel for.08-25-S
connectors and are used for I/O signals to the system peripheral devices such
as:
(1) Serial Printers
(2) Video Terminals
(3)
Parallel I/O Printer
(4) Acoustical Coupler or Modems
Each installation will vary depending upon the selection of peripheral devices
and the applications programs in use. Three I/O ports are furnished as part of
the cpu. These are shown connected to the rear panel illustrated in Figure
2-2. In applications requiring additional ports, a Quadraport or an Octaport
may be installed into the S-lOO Bus and interconected to the rear panel. Both
the front and rear panels are secured to their respective bezel by 6-32 Kep
nuts. Each bezel is secured to the base plate by 6-32 screws. Both panel and
bezel may be easily removed for servicing or installation of additional I/O
ports in the field.
Card Cage -5-100 Bus
2.10
The card cage furnishes a rigid support structure for the S-IOO Bus
cards when they are inserted into the S-IOO Bus. The Motherboard PC Assembly
contains 12 S-IOO Bus receptacles or jacks, Jl through J12. Each jack has. 100
separate pins. The actual bus consists of 100 parallel traces on the pc board
connecting the same pin on each jack. Each line has a ground trace between it
and the adjacent line to minimize coupling between signal lines.
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5505 Technical Manual 404512
2.11 The 8-100 Bus lines are described by function in Part 3 of this
manual. Physically they make up five groups:
(1) Power and common lines. These are connected to the power supply module
discussed in 2.17. 8ix lines.
(2) Address lines. 16 lines.
(3) Data In and Out lines. 16 lines.
(4) Control 8ignal lines. 40 lines.
(5) Dynabyte Reserved lines. 22 lines.
The Motherboard PC Assembly also contains a few discrete components which make
up the Halt Detector. The Halt Detector and Reset line are connected to the
front panel by a four-conductor receptacle, J13, connected to plug, P13,
mounted at the front edge of the Motherboard PC Assembly.
5-100 Bus Cards
2~12 Dynabyte 5-100 Bus cards are pc assemblies normally measuring 5 x 10
inches. A laO-pin edge connector mates with the 8-100 Bus connector on the
motherboard. This connector is offset by 5/8 inch from the card centerline,
i.e., an 8-100 Bus card cannot be inserted into a jack backwards.
2.13 Dynabyte 8-100 Bus
cards may have one or more on-board regulators for
regulating and distributing the dc power supply voltages from the bus to the
logical elements on the card.
NOTE
An 5-100 Bus card should never be inserted
or removed from the bus when the ac 1 ine
power is on.
2.14 A solder mask is applied to the component and non-component sides of
the pc boards when it is manufactured and before it is loaded with components.
This mask covers all surfaces except:
(1) The 100 gold-plated fingers of the edge connectors,
(2) Each of the plated-through holes.
The solder mask assures there will be no bridges between traces. The soldering
operation can then only take place. at a hole where normally solder joins a
component
lead and a pad.
2.15 Dynabyte 8-100 Bus cards usually provide sockets for most multi-lead
active devices to facilitate fault location and servicing.
2.16 Options for Dynabyte 8-100 cards are provided by three m~thods:
(1) Dual-In-Line packaged (DIP) switches of one to nine poles, 8PST, are
normally used in functions which may have to be set to the user's individual
DYNABYTE -Page 11

5505 Technical Manual 404512
installation.
(2) Bare wire straps are soldered into the pc board for options Which are
installed at the factory. These are not to be changed in the field except by
instructions from Dynabyte Customer Support or When specified in the
individual Dynabyte S-100 Bus Card Technical Manual.
IMPORTANT
Never change the settings of an Option Switch without
referring to the Option Switch Tables in the individual
Dynabyte 8-100 Bus Card Technical Manual.
(3)
Instructions are written into a programmable read-only memory (PROM) at
the Dynabyte factory, resulting in a read-only memory (ROM). In some
applications a ROM can be phantomed" into a desired range of addressed RAM.
Phantoming means a memory segment can replace another under program control.
When the 5505 is set to POWER ON or RESET is operated, the CPU jumps to the I
starting address of the disk controller ROM. The ROM boot instructions are
overlaid at the common address location. These instructions are for the CPU
to read Track 0, Sector 1 from Drive A. This particular operation is called
the ROM Boot. Track 0, Sector 1 contains additional instructions which are
loaded into-RAM and executed. These instuctions cause the CPU to read the
Dynabyte Disk Operating System from the diskette or disk. This second
operation is called the Disk Boot. The ROM is then switched out.
NOTE
Dynabyte ROMs are individually marked with a Dynabyte part
number. The part number represents an individual program
for a specific equipment configuration. The ROM part
numbers are tabulated for various equipment configurations
in the specific 8-100 Bus Card Technical Manual.
Changes
in options of this type are made by exchanging the particular ROM.
ROMs are only available from Dynabyte.
2.17 Dynabyte S-lOO Bus cards carry a distinctive White silkscreened
marking on the component side of the pc assembly.
(1)
The card name and part number. This facilitates board identification
and referencing for reordering, servicing and referencing the appropriate
Dynabyte S-lOO Card Technical Manual, schematic or replaceable parts list.
(2) Component reference designators are marked When practical. They
facilitate locating the individual part on a schematic or parts list.
Most Dynabyte PC assemblies derive the major component reference designators
from a row-column matrix silkscreened onto the pc board. For example, rows
are A to 0 and columns are 1 to 18 on the 64K RAM card. An integrated
DYNABYTE -Page 12

5505 Technical Manual
404512
circuit located in the upper left corner is Al and the one located in the
lower right corner is 018.
Table
2-3 -- 5505 Computer, Interior Major Assemblies
Element
Axial Fan
Power Supply M:>dule
807392
Card Cage and S-IOO Bus
PC Assembly 800038
Front Panel Indicator
Connector J13
Front Panel Power
Connector
CPU I/O Cable 800285
Floppy Ma in Aux
Rear Cable 807658
Random Access Memory
PC Assembly 800589
CPU PC Assembly
803439
FUnction
Provides forced air cooling to the power
supply module and internal heat dissipating
pc assemblies.
Accepts 115 or 230 Vac, 50-60 Hz and supplies
the following preregulated voltages to the
S-IOO Bus and other assemblies:
(1) +16 Vdc
(2) +12 Vdc
(3) + 8 Vdc
(4) + 5 Vdc
(5) Power Supply cornmon
(6) -16 Vdc.
Provides 12
pc assembly positions. Power and
signal busses are tabulated by function in
Table 7-1.
A four-position connector Which provides a
connection point for the cable to the POWER
ON, HALT indi~ators and the RESET switch on
the front panel.
A two-position connector Which provides a
connection point for the cable to the POWER
ON switch on the front panel.
Provides for the interconnection of data,
status and control between the CPU PC
Assembly and the rear panel I/O ports. Refer
to Table 2-2, Key 6, 7 and 8.
Provides for the interconnection of data,
status and control between the Floppy Con-
troller PC Assembly and the Rear Panel Disk
I/O receptacle. Refer to Table 2-2, Key 9.
Provides storage for the Operating System,
Application Program and variables during
program execution.
Provides a central processor, interrupt logic,
two serial I/O ports and one parallel I/O
port.
DYNABYTE -Page 13

5505 Technical Manual
Disk Controller PC
Assembly 807525
Winchester
Controller
PC Assembly 807677
Cabinet Louvers
Auxiliary Controller
807506
5.25 Floppy Drive to
Aux Cable 807639
Data
Separator Card
807243
Provides the logic, status registers and ROM
bootstrap to support the Dynabyte diskette
drive.
Provides the logic, status registers and data
buffer to support the hard disk drive.
Provides air inlets for drawing air into the
cabinet for ventilation.
404512
Provides
the specialized electrical functions
for:
(1) 5.25 inch diskette drives
(2) 8.00 inch diskette drives
option strapping allows the Disk Controller,
Key 10 above, to work with both types of
media.
Provides for supplying I/O signals to the
drive module.
Converts data in a disk format to data
readable by the Winchester Controller.
2.18 Input/Output (I/O) Signals not affecting the S-lOO Bus are transferred
over special multi-pin connectors normally located at the top of the pc
assembly. Cable harnesses which mate with these connectors are normally made
up of flat multi-pair or flat twisted multi-pair cable.
Power Supply Module
2.19 The power supply module is located at the rear of the 5505 cabinet
between the card cage and the rear panel. The power supply operates on 115 or
230 Vac, 50 or 60 Hz line, optioned internally by straps. It utilizes a phase-
controlled regulator to provide ac line and load regulation. The supply
operates at relatively high efficiency and utilizes a minimum of components
resulting in high reliability. The ac chassis wiring to the power supply
module includes an EMI filter to minimize radiation of power supply switching
transients over the ac line.
Diskette Drive
2.20
The Diskette Drive is mounted at the right front of the chassis. Power
for this module is furnished from the 5505 power supply module.
Winchester Drive
2.21 The Winchester Hard Disk is mounted at the right front of the chassis.
Power for this module is furnished from the 5505 power supply module.
DYNABYTE -Page 14

5505 Technical Manual 404512
3. FUNCTIONAL DESCRIPTION
3.01 Part 3 will furnish the user with an overview of the 5505 Computer and
the 5-100 Bus. Detailed information on individual Dynabyte 5-100 cards is
provided in its technical manual.
NOTE
An * suffix to a signal name indicates
logical NOT and active low.
3.02 Figure.3-1 illustrates the 5505 computer in block diagram. It should
be used in conjunction with the schematic diagrams in Part 7 to familiarize
the user with the circuits. The 5505 Computer chassis can be divided into four
logical sections:
(1) Ope~ational Controls
(2) Power Supply M:>dule
(3) 5-100 Bus
(4)
5.25 inch Diskette Drive
(5) 5.25 inch Winchester Hard Disk Drive
3.03 Two operation controls are provided on the 5505 Computer.
(1)
The POWER switch applies ac line voltage to the fan, ac convenience
receptacle and power supply module. The POWER ON indicator is lit \IA1en the
power supply module outputs nominally +8 Vdc.
(2) The
RE5ET switch pulls the Reset line, Pin 75, of the 5-100 Bus low to
initiate a restart of the CPU, etc. The reset switch housing contains a
lamp and
indicates a halt when lit. A Halt Detector is part of the 5-100
Motherboard PC Assembly. This detector monitors the HLTA line, Pin 48. When
this status line goes high, a HLT instruction has been executed. The HALT
indicator is lit.
3.04 The Power SUpply Module converts ac line voltage to low dc voltages for
the 5-100 Bus and monitoring circuits. It provides regulation against ac line
fluctuations and load variations of the 5-100 Bus. The output voltages are
nominally:
(1) +16 Vdc
(2) +12 Vdc
(3) + 8 Vdc
(4) + 5 Vdc
(5) -16 Vdc.
DYNABYTE -Page 15

5505 Technical Manual 404512
One adjustment, R2 on the M:>dulator PC Assembly and part of the power supply
module, is used to set the +8 Vdc supply output voltage. The other voltages
are nominal and track the +8 Vdc. Refer to Figure 6-2 for the tolerance range.
3.05 Regulation is provided by a triac modulating the ac line applied to
the low voltage power transformer. The +8 Vdc output line is monitored and a
feedback
loop is used to control the conduction of the triac resulting in
phase-controlled regulation.
3.06 The +16, +8 and -16 output voltages are passively filtered. Ripple on
the +8 Vdc line is 0.3 to 1 Volt. The +5 and +12 voltages are set and
controlled by three-terminal regulators. These two voltages power the diskette
and hard disk drives.
3.07 The S-IOO Bus system consists of a set of signal lines used to carry
all information, interface messages and device-dependent messages among
interconnected devices.
3.08 The bus structure is organized into seven sets of signal lines: Refer
to Table 7-1 for descriptions of the following.
(1 ) Data Lines
(2) Address Lines
(3)
Status Bus
(4)
Control Output
(5)
Control
Input Bus
(6 ) Vectored
Interrupt Bus
(7 )
Utility Bus.
DYNABYTE -Page 16

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5505 Technical Manual
404512
NOTE
In and Out References are in respect to the CPU.
3.09 The data bus consists of 16 lines grouped as two unidirectional 8-bit
busses for byte operations.
(I) Data output appears on the data output bus DOO - D07. D07 is the most
significant bit.
(2) Data input appears on the data input bus DIO -DI7. DI7 is the most
significant bit.
3.10 The address bus consists of 16 signal lines used to select a specific
location in memory or a specific input/output device for communications during
the current bus cycle. The memory address bus consists of 16 lines specifying
1 of 64K memory locations. These 16 lines are named AO through A15, Where A15
is the most significant bit. The I/O device address bus consists of lines, AO
through A7, specifying 1 of 256 I/O devices, with A7 used as the most
significant bit. Address lines A15 - A8 are used as an I/O address modifier in
specific cases, i.e., the Octaport.
3.11 The status bus consists of nine lines that identify the nature of the
bus cycle in progress and qualify the nature of the address on the address
bus. The mnemonics for status lines always begin with a lo~r case sand
consist of:
(I)
Memory Read -- sMEMR
(2)
Op-Code Fetch -- sMl
(3)
Input -- sINP
(4)
Output - sOUT
(5)
Write Cycle -- sWO*
(6)
Interrupt Acknowledge -- sINTA
(7)
Halt Acknowledge -- sHLTA
(8)
Memory Request -- sMREQ*
(9)
Memory Refresh -- sRFSH*
3.12 The lines of the control output bus dete~ine the timing and movement
of data during any bus cycle. The mnemonics for the control output lines
always begin with a lo~r case p. The four lines are:
(I) pSYNC*, which indicates the start of a new bus cycle.
(2) pDBIN, a generalized read strobe that gates data from an addressed
slave onto. the data bus.
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5505 Technical Manual 404512
(3) pWR*, a generalized write strobe that writes data from the data bus
into an addressed slave.
(4) pHLDA, the hold acknowledge signal that indicates to the highest
priority temporary master that the pennanent master is relinquishing control
of the bus.
3.13 The five lines of the control input bus allow bus slaves to
synchronize the operations of bus masters with conditions internal to the bus
slave, e.g., data not ready, and to request operations of the permanent
master, e.g., interrupt or hold. The five control input lines are:
(1) ROY
(2) XRDY
(3) INT*
(4) NMI*
(5) HOLD*
The ready lines are used by bus slaves to synchronize bus masters to the
response speed of the slave. Thus cycles are suspended and wait states
inserted until both ready lines are asserted. The ROY line is the general
ready line for bus slaves. It is specified as an open collector line. The XRDY
line is a special ready line used by test devices to stop and single-step bus
masters. It is not specified as an open collector line and should not be used
by
other bus slaves since a bus conflict may exist.
3.14 . The two interrupt lines INT* and NMI* are. used to request service from
the perma~ent b~s master. The INT* line may be masked off by the bus master,
~sually VIa an Internal software geqeratiQn. If the bus ma~ter accePts the
Interrupt request on the INT* lIne, It may respond WIth an Interrupt
acknowledge bus cycle accepting vectoring information from the data bus.
3.15 The NMI* line is a nonmaskable interrupt request line, that is, it may
not be masked off by the bus master. Accepting an interrupt on the NMI* line
will not generate an interrupt acknowledge bus cycle. An interrupt request on
the INT* line is asserted as a level, that is, the line is asserted until
interrupt service is received. An interrupt request on the NMI* line, on the
other hand, is asserted as a negative-going edge, since no interrupt
acknowledge cycle will be generated. Both lines are specified as open-
collector lines.
3.16 The hold request line, HOLD *, is used by temporary bus masters to
request control of the bus from the permanent bus master to prevent temporary
masters from gaining bus control. The HOLD* line is specified as an open
collector line and may only be asserted at certain times.
3.17 The eight lines of the vectored interrupt bus are used in conjunction
with the generalized vectored interrupt request, INT*, to arbitrate among
eight levels of interrupt request priorities. The eight lines of the vectored
interrupt bus are VIO* through VI7*, where VIO* is considered the highest
priority interrupt. The vectored interrupt lines should be implemented as
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