NorthStar HORIZON Random Access Memory User manual

North Star Computers, Inc.
14440 Catalina St., San Leandro, CA 94577 USA
[phone] TWX/Telex [phone]
HRAM
HORIZON Random Access Memory
USER/ TECHNICAL MANUAL
HORIZON is a registered trademark of North Star Computers, Inc.
Copyright © 1981, by North Star Computers, Inc. All
Rights Reserved
004068

HRAM USER/TECHNICAL MANUAL
This manual was digitally remastered by Howard M. Harte, June 2003.
http://www.hartetec.com
If you find any errors, please email [e-mail].

HRAM USER/TECHNICAL MANUAL
CONTENTS
Section Page___
1 INTRODUCTION
1.1 General Description 1-1
1.2 Warranty Information 1-1
1.3 Specifications 1-3
2 INSTALLING AND REMOVING THE HRAM
2.1 Installation 2-2
2.2 Removal 2-3
3 IMPLEMENTING HRAM OPTIONS
3.1 Example Memory Configurations 3-3
3.1.1 Example 1: Three Banks 3-3
3.1.2 Example 2: Three Banks 3-5
3.1.3 Example 3: Four Banks 3-6
3.2 Bank Switching 3-7
3.2.1 Designating Switched Areas 3-7
3.2.2 Designating I/O Port Control Bit 3-9
3.2.3 Software Instructions 3-10
3.2.4 Bank Status on Reset 3-11
3.3 Memory Address Switches 3-13
3.3.1 Revision B Board 3-13
3.3.2 Revision E Board 3-14
3.3.3 32K Board 3-18
3.4 First Quadrant Option (Revision E Board only) 3-19
3.5 Parity Checking 3-20

HRAM USER/TECHNICAL MANUAL
Section Page___
3.5.1 Designating I/O Port Control Bits 3-20
3.5.2 Designating Parity Error Response 3-21
3.5.3 Software Instructions 3-22
3.6 Board and Schematic Revision Levels 3-22
4 TESTING THE HRAM
5 THEORY OF OPERATION
5.1 Overview 5-1
5.2 Address Multiplexer 5-2
5.3 Refresh Logic 5-3
5.4 Port CO Detector 5-4
5.5 Address Latch 5-4
5.6 Address Decoder 5-4
5.7 Jumper Area JP1 5-5
5.8 Bank and Parity Logic 5-5
5.9 Strobe Generator 5-6
5.10 Voltage Regulators 5-9
6 TROUBLESHOOTING
6.1 Check HRAM Seating 6-1
6.2 Change Board Slots 6-2
6.3 Check HRAM Configuration 6-2
6.4 Run Diagnostic Programs 6-2
6.5 Replace HRAM 6-3
6.6 Repair Procedures 6-3

HRAM USER/TECHNICAL MANUAL
APPENDICES
A RAM Chip Location Chart A-1
B Bus Signals Used by HRAM B-1
C HRAM 64K - Parts List C-1
D HRAM 64K – Schematics D-1
E Reader Response Form E-1

HRAM USER/TECHNICAL MANUAL

HRAM USER/TECHNICAL MANUAL
INTRODUCTION 1
This manual supplies the user of the HORIZON Random
Access Memory (HRAM) board with information he or she
needs to install the board and put it into operation.
This includes information on selecting the various
memory options, testing the board and resolving any
difficulties associated with system integration.
The manual also provides information for service
technicians and engineers who may wish to evaluate the
technical aspects of the board or to undertake its
repair.
1.1.1 GENERAL DESCRIPTION
The HRAM board is a random access memory board
designed for use in the HORIZON computer system.
There are three versions of the HRAM board: HRAM-64
with 64K bytes, HRAM-48 with 48K bytes; and HRAM-32
with 32K bytes. The only significant difference
between these boards is the amount of memory they
contain. All three versions incorporate parity error
checking and bank switching capabilities.
1.2 WARRANTY
North Star Computers, Inc., warrants the electrical
and mechanical parts and workmanship of this product
to be free of defects for a period of 90 days from
date of purchase. If such defects occur, North Star
Computers, Inc. will repair the defect at no cost to
the purchaser. This warranty does not extend to
defects resulting from improper use or assembly by
purchaser, nor does it cover transportation to the
factory. Also, the warranty is invalid if all
instructions included in the accompanying
documentation are not carefully followed.

HRAM USER/TECHNICAL MANUAL
Should a unit returned for warranty repair be deemed
by North Star Computers, Inc. to be defective die to
purchaser's action, then a repair charge (not to
exceed $50 without purchaser's consent) will be
assessed. ANY UNITS) OR PART(S) RETURNED FOR WARRANTY
REPAIR MUST BE ACCOMPANIED BY A DATED COPY OF THE
ORIGINAL SALES RECEIPT. The item should be returned to
the dealer from whom the product was purchased, for
implementation of the warranty. When sending the item
to the factory for repair, the dealer must call the
North Star Technical Hotline to receive a Return
Material Authorization (RMA) number to accompany the
item to the factory.
The following warranty limitation applies to units
located outside the United States of America: All
costs and arrangements for transportation of the
product to and from the factory are borne entirely by
the customer.
No warranty, expressed or implied, is extended
concerning completeness, correctness, or suitability
of the North Star equipment for any particular
application. There are no warranties which extend
beyond those expressly stated herein. This limited
warranty is made in lieu of all other warranties,
expressed or implied, and is limited to repair or
replacement of the product.

HRAM USER/TECHNICAL MANUAL
1.3 SPECIFICATIONS
The HRAM specifications are given in Table 1-1.
Table 1-1
HRAM Specifications
Storage
Capacity
32K bytes for the HRAM-32
48K bytes for the HRAM-48
64K bytes for the HRAM-64
Bits per Byte Eight data bits and one parity
bit.
Access Time 300 ns typical

HRAM USER/TECHNICAL MANUAL

HRAM USER/TECHNICAL MANUAL
INSTALLING AND REMOVING THE HRAM 2
CAUTION
The electronic components on the HRAM board
may be damaged by the static electricity
which often builds up in the human body.
Before touching the HRAM board, discharge
this electricity by touching a grounded
metal object, such as the chassis of a
Horizon which is plugged into the wall
outlet. Follow this procedure each time the
board is handled.
If the HRAM was packaged separately from the
HORIZON, examine the contents of the carton to make
sure they match the packing slip. Check to see if
anything appears to be damaged due to shipping.
When handling the board, touch it only by the edges,
to avoid contact with the sensitive components (see
Figure 2-1). When laying the board down, place it on
a flat surface with the components facing up.
Holding the HRAM
Figure 2-1
WARNING
DO NOT REMOVE THE COVER FROM THE HORIZON
UNTIL THE POWER IS OFF, THE FAN HAS
STOPPED, AND THE RED INDICATOR LIGHT ON THE
FRONT PANEL HAS COMPLETELY DIMMED. DO NOT
TURN THE POWER BACK ON UNTIL THE COVER HAS
BEEN REPLACED.

HRAM USER/TECHNICAL MANUAL
2.1 INSTALLATION
To install the HRAM in the HORIZON, hold the memory
board in one hand and touch the metal chassis of the
HORIZON with the other hand as shown in Figure 2-2.
This will eliminate any difference in static potential
between the memory board and the computer.
Discharging Static Electricity
Figure 2-2
Hold the board by both edges, with the component side
of the board toward the front of the computer. Slide
the board into any empty slot in the HORIZON as shown
in Figure 2-3.
Installing the HRAM
Figure 2-3
The row of metallic strips, or "fingers" on the bottom
of the board should f it into the connector at the
base of the card slot. Press firmly on the top of the
memory board until the board is firmly seated in the
connector.

HRAM USER/TECHNICAL MANUAL
2.2 REMOVAL
WARNING
NEVER REMOVE THE HRAM BOARD UNTIL THE
POWER IS COMPLETELY OFF IN THE
HORIZON.
To remove the HRAM, grasp the upper edge of the board.
Avoid putting excessive pressure on the board
components, and be careful of the sharp wire tips that
project out of the back of the board. Pull the board
out, and lay it down on a flat surface.

HRAM USER/TECHNICAL MANUAL

HRAM USER/TECHNICAL MANUAL
IMPLEMENTING HRAM OPTIONS 3
HRAM options are implemented by inserting and removing
mini jumper plugs at various locations on the PC board
and by changing the setting of the Memory Address
switches. Figure 3-1 shows the locations of the jumper
areas and the address switches on a 64K revision E
board. Other boards differ as follows:
1. Jumper areas JP4 and JP6 do not exist on revision B
boards.
2. Switch S2 is not installed on 48K revision B
boards.
Instructions for determining the revision level of the
HRAM board are given in Section 3.6.

HRAM USER/TECHNICAL MANUAL
Jumper Plug Areas and Memory Address Switches
Component
S1, S2 - Select the active memory areas.
JP1 - Selects the bank status on reset and selects
I/O control bits for bank switching and
parity.
JP2 - Selects areas to be bank switched.
JP3 - Selects the parity error response.
JP4 - Implements the First Quadrant option.
JP6 - Reserved for future use. Do not install
a jumper plug at this location.
Figure 3-1

HRAM USER/TECHNICAL MANUAL
The jumper areas consist of clusters of pins protruding
from the PC board. When a jumper plug is plugged onto a
pair of adjacent pins, it connects the pins together.
The jumper plugs are used to select various options on
the HRAM Board as described in Sections 3.2, 3.4 and
3.5.
Each of the Memory Address switches, S1 and S2,
actually a group of eight switches in a single package.
These switches are used as described in Section 3.3.
CAUTION
To reposition the jumper plugs, you must
remove the HRAM from the HORIZON. Make sure
the power is turned off and the red light on
the front panel is completely out before you
remove the HRAM.
To reconfigure the jumper plugs, lay the HRAM board
down on a flat surface with the components facing up.
You can move the jumper plugs with your fingers or a
pair of long nose pliers.
To reposition the jumper plugs, you must remove the
HRAM from the HORIZON. Make sure the power is turned
off and the red light on the front panel is completely
out before you remove the HRAM.
To reconfigure the jumper plugs, lay the HRAM board
down on a flat surface with the components facing up.
You can move the jumper plugs with your fingers or a
pair of long nose pliers.
EXAMPLE SYSTEM CONFIGURATIONS
This section shows the correct positions of the Memory
Address switches and the jumper plugs for several
example configurations of the HORIZON system.
3.1.1 EXAMPLE 1: THREE BANKS
In this example, the HORIZON contains three HRAM-64
Revision B boards, a standard Micro-Disk Controller
board at E800H, and a Floating Point board at EFFOH.
The switches and jumper plugs are shown in Figure 3-2.
On board 1, the memory between EOOOH through E7FFH and
FOOOH through FFFFH is left on permanently, to contain
the resident operating system. On the other two boards,
the whole last 8K of address space (EOOOH through
FFFFH) must be disabled, to prevent interference with
the Micro-Disk Controller, the Floating Point board,
and the 6K that contains the resident operating system.

HRAM USER/TECHNICAL MANUAL
In this case, the system contains three banks with the
maximum 56K apiece and a resident operating system of
6K that is always left on. Each bank is switched off
and on as a single unit. Bank 1 is configured to be
turned on after the system is powered up or reset.
Banks 2 and 3 are configured to be turned off after
the system is powered up or reset.
Parity error checking is left in the standard North
Star configuration.
Example 1
Figure 3-2

HRAM USER/TECHNICAL MANUAL
3.1.2 EXAMPLE 2: FOUR BANKS
In this example, the HORIZON contains one HRAM-48
board, three HRAM-32 boards, and a standard Micro-Disk
Controller board at E8OOH. All HRAM boards are
revision B. The switches and jumper plugs for this
example are shown in Figure 3-3.
The 48K board is partitioned into two segments, OOOOH
through 7FFFH, and 8000H through BFFFH. An operating
system that requires 16K of memory is loaded into the
region between 8000H-BFFFH. This segment is always
turned on. The other segment of this board is bank
switched, and is designated the bank to be turned on
when the system powers up or resets.
All three 32K boards have their memory starting at
OOOOH. All are bank switched off and on as single
units, and all are programmed to be turned off when
the system is powered up or reset.
Parity checking is left in the standard North Star
configuration.

HRAM USER/TECHNICAL MANUAL
Example 2
Figure 3-2