Vector Graphic Bitstreamer II User Manual

:lit)t=tiCAli1iC=I

JI

U)E=I) mAnUAL

BITSTREAMER II BOARD

Revision 1

USER'S MANUAL

Revision A

January

1, 1980

Copyright

198~ by

Vector Graphic Inc.

All rights reserved.

Disclaimer
Vector Graphic makes no representations or warranties with respect to the
contents of this manual itself, \\bether or not the product it describes is

covered

by

a warranty or repair agreement. Further, Vector Graphic reserves
the right to revise this publication and to make changes from time to time
in the content hereof without obligation of Vector Graphic to notify any

person of such revision or changes, except \\ben an agreement to the contrary
exists.

Revisions
The date and reV1Slon of each 'page herein appears at the bottom of each
page. The revision letter such as A or B changes if the MANUALhas been.

improved but the PRODUCTitself has not been significantly modified. The

date and revision on the Title Page corresponds to that of the page most

recently revised. When the product itself is modified significantly, the

product will get a new revision number, as shown on the manual's title page,
and the manual will revert to revision A, as if it were treating a brand new
product. EAai MANUALSHOULDONLYBE USEDWITHTHEPRODOCTIDENTIFIEDONTHE

TITLE PAGE.

'Ibe Bitstreamer II Board sold hereunder is sold "as is", with all faults and
without any warranty, either expressed or implied, including any implied
warranty of fitness for intended use or merchantability. However, the above

notwithstandi1'l3,VEC1'OR GRAPHIC, INC. ,will, for a period of ninety (90)
days following delivery to customer, repair or replace any Bitstreamer II
Board that is found to contain defects in materials or workmanship,
provided:

1. Such defect in material or workmanship existed at the time the

Bitstreamer II Board left the VECTOR GRAPHIC, INC., factory;

2. VECTOR GRAPHIC, INC., is given notice of the precise defect

claimed within ten (10) days after its discovery;

3. The Bitstreamer II Board is promptly returned to VECTOR GRAPHIC,

INC., at customer's expense, for examinationbyVECTOR GRAPHIC, INC., to

confirm the alleged defect, and for subsequent repair or replacement if

found to be in order.

Repair, replacement or correction of any defects in material or workmanship

which are discovered after expiration of the period set forth above will be

performed

by

VECTOR GRAPHIC, INC., at Buyer's expense, provided the

Bitstreamer II Board is returned, also at Buyer's expense, to VECTOR

GRAPHIC, INC., for such repair, replacement or correction. In performing

any repair, replacement or correction after expiration of the period set
forth above, Buyer will be charged in addition to the cost of parts the

then-current VECTOR GRAPHIC, INC., repair rate. At the present time the
applicable rate is $35.00 for the first hour, and $18.00 per hour for every
hour of work required thereafter. Prior to commencing any repair,

replacement or correction of defects in material or workmanship discovered

after expiration of the period for no-cost-to-Buyer repairs, VECTOR GRAPHIC,

INC., will submit to Buyer a written estimate of the expected charges, and

VECTOR GRAPHIC, INC., will not commence repair until such time as the
written estimate of charges has been returned by Buyer to VECTOR GRAPHIC,

INC., signed by duly authorized representative authorizing VECTOR GRAPHIC,
INC., to corrunence

wit.11

the repair work involved. VECTOR GRAPHIC, INC.,

shall have no obligation to repair, replace or correct any Bitstreamer II

Board until the written estimate has been returned with approval to proceed,

and VECTOR GRAPHIC, INC., may at its option also require prepayment of the

estimated repair charges prior to c~ncing work.

Repair Agreement void if the enclosed card is not returned to VECTOR

GRAPHIC, INC. within ten (10) days of end consumer purchase.

This manual is intended for computer
distributors, or others with at least a
moderate technical knowledgeof small
computers.

It will describe what the Vector Graphic
Bitstreamer II Board does in the context
of a computer system, howto use the board

both in Vector Graphic and in other

5-10(3

systems, and howthe board circuitry ¥.Orks.

Each section is written at a uniform level
of technical depth. "Perspective" describes

WHATthe board does and requi res only a

rooderate knowledgeof computer design.
Most other sections tell

HCNl

to makeit do

things and assl1!t"esthe same level of
knowledge, plus the ability to solder

jumpers and flip switches. "Theory of

Operation" discusses WHYthe board ¥.Orks
and assumesa knolwedgeof digital

electronics.

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

1.1".1

1.11

Introduction ••••••••••••••••••••••••••••••••••••••••••••••• 1-1

Serial channels generally •••••••••••••••••••••••••••••••••• 1-1
Serial asynchronous communication •••••••••••••••••••••••••• 1-2
Serial synchronous communication ••••••••••••••••••••••••••• 1-2

Interrupt driven serial channels ••••••••••••••••••••••••••• 1-3

RS-232C theory ••••••••••••••••••••••••••••••••••••••••••••• 1-4

RS-232C on the Bitstreamer II •••••••••••••••••••••••••••••• 1-5
2~

mA current

loop•••••••••••••••••••••••••••••••••••••••••

1-7

Real time clock interrupts ••••••••••••••••••••••••••••••••• 1-7
Interrupt vectors and priority ••••••••••••••••••••••••••••• 1-8

Parallel channels •••••••••••••••••••••••••••••••••••••••••• 1-9

Table 1 - Board Address Jumpers •••••••••••••••••••••••••••• 2-2
Table 2 - Functions of I/O Addresses and Connectors Used •••2-2

2.2 Asynchronous serial baud rate selection •••••••••••••••••••• 2-3

2.3 How to connect most RS-232C serial terminals and printers ••2-4

2.4 .How to connect many low speed asynchronous acoustic

couplers and modems ••••••••••••••••••••.••••••••••••••••••• 2-7

2.5 Connecti~ additional RS-232C handshakill3 lines •••••••••••• 2-8
Table 3 - RS-232C and Connections on Bitstreamer II Board ••2-9

Table 4 - Jumper Areas for Each Serial Channel ••••••••••••• 2-ll
Table 5 - 8251 Pins in Jumper Areas •••••••••••••••••••••••• 2-l1

Table 6 - RS-232C Lines Available in Jumper Areas, and

Pads Connected to +12 VDC •••••••••••••••••••••••• 2-12

Table 7 - Installill3 a 1488 Quad Line Driver or a

1489 Quad Line Receiver, in a Spare Socket ••••••• 2-l4

2.6 How to connect 20 IDA current loop •••••••••••••••••••••••••• 2-l5

2.7 How to modify the board to generate interrupts ••••••••••••• 2-l5
Table 8 - Interrupt Jumper Pads and Mask Bits •••••••••••••• 2-l5

Table 9 - 8~80 Restart Instructions and Jumpering •••••••••• 2-l7
Table 10- Data Bus Bytes Generatedbya Jumper in Area L •••2-18
Table 11- VI Lines Available in Area K ••••••••••••••••••••• 2-l9

Table 13- Spare Inverters in U2l ••••••••••••••••••••••••••• 2-2l
Table 14- Spare Open Collector NAND Gates in Chip U10 •••••• 2-2l

III. Theory of Operation

3.1 Serial

cha.nn.els •••••••••••••••••••••••••••••••••••••••.•••••

3-1

3.2 Parallel input channels •••••••••••••••••••••••••••••••••••• 3-l

3.3 Parallel output channels ••••••••••••••••••••••••••••••••••• 3-2

3.4 Interrupts•••.••.•••••••.•••••.•••••••.•.•.••••.•..•••••.•.3-2

Board layout
Schematic errata
Schematic

Purpose Multiple serial and parallel input/ouput.
Compatibility S-1~0 systems.
serial channels 3, using

8251

controller chips.

Channel addresses x2 and x3, x4 and x5, x6 and x7 where x is any digit

o

to 7. Prewired x is 0. (Each serial channel uses

two I/O addresses.)
Signal levels EIARS-232C,or 201Mcurrent loop on one channel only.
RS-232handshaking Lines 5, 6, and 8 are held high.

Other handshaking lines are not connected•

.Jumperpads are provided to connect than.

There is one spare recevier and one spare driver for

handshaking lines on board that can be connected by

jumper. '!here are two spare slots if rooreare needed.

Can be wired for internal or external gynch.

8251 SYNDETline is not connected.

Not nowconnected to the external ~rld as required

for synchronous operation.

Single or double synch character can be programmedfor

each channel independently.

TTL

(input

= 1 'ITL

load; output drives 5

TTL

loads).

8 input, 8 output for each channel.
+5 VDC, +12 VDC, -12 VDC, and GND are also provided

for each channel.
Over l00K bytes/second.
Optional. Has 34-pin female connector and 34-line

ribbon cable. No connector is at the other end,
allowing user to configure as required. Must be
ordered separately.

If you are using the USARTs on the board as sources
of interrupts, you cannot use the output side of
Parallel O1annel A for normal parallel output.

Interrupts can be generated fram any combinaton of

the 3 USART RxRDY's, 3 TxRDY' s, and a 55 Hz real time
clock. Jumper pads provided. None prewired.

Output to parallel channel A selects (masks) interrupt

sources previously wired in.
Dummy input from Parallel Channelaresets 55 Hz real

t~e clock interrupt line during an interrupt service

routine. However, Parallel Channel B can be used for
normal input (and output) as well.

Can use 8080, 280 Mode 0, 280 r~de I, or 280 Mode 2

A Bitstreamer II board can generate one of 9 possible

bytes in response to an interrupt, including

three of the restart instructions for usewith 8080
and Z80 Mode 0 interrupts. Software polls to

determine which possible source on a Bi tstreamer II

board is the actual source of the interrupt.

S-100 interrupt bus Pads are provided for jumpering interrupt sources to

the S-100 VI lines.
+8 Vdc@720 mA typical.

+16 Vdc@30

IDA

typical.

-16 Vdc@30 IDA typical.

The Vector Graphic Bi tstreamer II Board is an all-purpose input/output

board for S-l~~ systems. It offers three serial I/O channels and 2 8-bit

parallel input/output channels for interfacing with multiple peripheral

devices such as printers, modems, and terminals. It also offers a 55 Hz

real-time clock which can interrupt the CPU for functions such as sharing of
the CPU by several users or peripherals.

We will use the term "channel" rather than "port" to avoid confusion

causedbythe fact that each serial channel makes use of two I/O addresses,
which are often called I/O "ports."

The CPU sends data to the serial and parallel charmels via I/O addresses.

The I/O addresses used by the board can be changed as a group. The board

uses the eight I/O address x2 to x9 (in hexadecimal notation), where x is

any dig it from 0 to 7. You specify the value of x

by

jumper, as listed in
Table 1 in Section 2.1. Table 2 in Section 2.1" lists the function of each
of the eight I/O addresses, which are fixed relative to one another.

'!heBitstreamer II Board does not come wi th any software for specific

applications, though Vector Graphic supplies certain items of software that

make use of its featues.

The three serial channels center around three industry standard 8251

USART (Universal Synchronous/Asynchronous Receiver!Transmitter) chips. Much

of the flexibility of the Bitstreamer II board derives from the flexibility
of these chips, which can be modified via software. You, through software,
can control the rate of transmission, and the format of the transmitted
data. Data is transmitted as ASCII code having bet'II'Ieen5 and 8 bits per
character, with an optional added-on pari ty bi t (choice of even or odd), and
with one start bit and a choice of one, one and a half, or two stop bits per
character. Further, using the 825l's, the board can handle either
asynchronous or synchronous comm.mication. Each serial channel is entirely

independent of the others. Baud rates, format, handshaking, and whether
comnunication is asynchronous or synChronous, is specified independently for
each serial channel through software and in some cases hardware
modifications.

It is not within the scope of this manual to detail the functioning of
the 8251 USART chip, nor to teach the theory of serial communication. In
order to write your own communications software or to modify the Bitstreamer

II serial channels, you will need to be thoroughly familiar 'IIith this ch ip.
You can refer to Intel's App1 ication Note #16, entitled "Using The 8251
Universal SynchronOUS/Asynchronous Receiver/Transmitter," which Intel will

provide. This Note is also an excellent reference on basic communications.

theory. More readily available references on the

8251,

but ones that have

less to say about communication theory, are the "INTEL

8080

Microcomputer

Systems User's Manual," available either from Intel or most canputer retail

stores, and Adam Osborne's IIAnIntroduction to Microcomputers, Volume II -

Some Real Products,1I also available in many computer stores.

1.3 serial

asynchronous

coommication

Separately for each serial channel, you can select the rate of

transmission and reception from a choice of

110, 150, 300, 600, 1200, 2400,

4800,

or 9600 bits/second. You choose the rate using small dip-switches on

the board.

If you are writing custom software, there is in addition a simple way in

software to divide the chosen rate of a desired channel by 4, allowing some

control of the rate without physically opening up the computer. For

example, if you have a modem that is swi tch selectable for either

1200

bits/second or 300 bits/second, you can write a program that enables the
operator usi1'l3the keyboard to change the computer's rate of commun ication
to match that of the roodem at any given time.

Separately for each serial channel, you can select via software the

number of data bits in each ASCII character, selecting either 5, 6, 7, or 8.
You can also select the number of stop bits in each character, selecting

either 1, 1 1/2, or 2. Finally, you can select whether or not a parity bit

is included for each character, and if chosen, whether or not it is even or
odd parity. For how to do this in software, see the references given
earlier for the

8251

USART.

You can enable one or more serial channels to communicate in synchronous

mode. Modifications to the board will be required to accompl ish this. In

brief, the

8251

SYNDET pin and the TxC and RxC clock pins must be connected

to the outside world, which is not the case in the standard configuration of
the board.

Once set up for synchronous comnunication, you can select separately for
each such channel the rate of communication, by using an external clock
between" and 56K bits/second. As with asynchronous comrrunication, you can

select via software the character length, selecting either 5, 6, 7, or 8

bits. You can also select via software whether or not a parity bit is
included for each character, and if chosen, whether or not it is even or odd

parity. Also via software, you can select separately for each channel
wheG~er you are using internal or external synchronization, and whether one
or

t~

synch characters are used.

Interrupts can be generated from each of the three 8251 RxRDY pins, and

each of the three 8251 TxRDY pins. You can choose to generate interrupts

from one or any combination of these six signals. Jumper pads are provided

for wiring up the interrupt capability for each of these signals, as

described in Section 2.7.

The board requires that you specify in software which of the signals so
wired are to actually generate interrupts. This enables you to wire up
several of them, and then to dynamically control which ones generate
interrupts at any given time. This procedure is called "interrupt masking"
and uses an I/O address known as the "interrupt masking register.

n

For example, assume you are creating a software routine that outputs a

character to an 8251 whenever that 8251 is ready to transmit it, but you do
not want to poll the 8251 to determine when it is ready. Assume instead

that you want to arrange for the 8251 to interrupt some other routine

whenever the 8251 is ready to transmit. To do this, you would connect the
TxRDY pin of that 8251 to the interrupt line, as described in Section 2.7.
Now, as soon as you receive an interrupt, your software will branch to an

interrupt service routine which transmits a character. When it is finished
transmitting a character, you do not want to re-enable interrupts until you

are ready to transmit the next character, because otherwise, the 8251 will

tie up the CPU with TxRDY interrupts. The problem is that you do not want

to leave interrupts disabled because you want other peripherals such as the
keyboard to be able to interrupt. The way you solve this is to enable
interrupts, but also mask out the TxRDY interrupt using the interrupt

masking register until software is ready to transmit another character.

You must use the interrupt masking register whenever you are using the

8251's to generate interrupts. Even if you do not want to disable some of
the interrupt sources, you must enable them at the outset by initializing

the interrupt masking register appropriately.

The interrupt masking register is the output side of Parallel Channel A

on the Bitstreamer II Board. The parallel channels are discussed later in

Perspective. The precise way that the interrupt masking register is used

by software is discussed in Section 2.7. If you are using the 8251's as
interrupt sources, you cannot use the output side of Parallel Channel A for

any other purpose.

This manual cannot

describe the

RS-232C protocol in detail. For a full

description, obtain a copy of the RS-232C E~ STANDARD document, published
by Electonic Industries Association, Engineering Department, 2001 Eye

Street, N.W., Washington, D.C. 20006. Alternately, if you have access to
Data Pro or Auerbach reports on communications, they contain thorough
articles describing the protocol and its implications. The following

information, however, will be of bronediaterelevence in this manual:

An RS-232C signal can either be POSITIVE (+12 Vdc) or NEGATIVE (-12 Vdc) •

Positive is ON or SPACING, Negative is OFF or MARKING. RS-232C line drivers
typically invert these signals when they are converted to and from TTL

signals. Hence, RS-232C POSITIVE corresponds to

TIL

low (aboutaVdc) arid
RS-232C NffiATIVE corres~nds to TTL high (about 5 Vdc). (TTL is the kind of
signal used within the computer.)

An RS-232C cable consists of 25 lines. An RS-232C transmit or receive
data line carries a serial sequence of POSITIVE and NEGATIVE pulses that
correspond with the characters you want to transmit or receive. There is
also associated formating and parity information attached to the information

by

the communication device such as an 8251. In addition to the transmit
and receive data lines, there are ground lines, (lines 1 and 7), and there
are handshaking lines that are used

by

communication, terminal, and computer
equipment to inform each other of their status (lines 4, 5, 6, 8, 20, 22,
and a few others that are rarely used). The full RS-232C protocol also

specifies a set of rarely used "secondary" lines which have the same

definitions as some of the primary lines, but carry an independent set of

signals. Altogether there are 25 RS-232C lines defined, but most

applications use only a few of them.

In the real ~rld, very few devices require "full RS-232C" protocol. In

fact, very few devices even require all of the handshaking lines mentioned

above. Many require one or even none. Further, many devices use

handshaking lines differently than defined by RS-232C, violating the

protocol. In short, it is confusing at this time to say that a given device

requires "full RS-232C." You must specify exactly what signals it sends and

expects to receive on each line.

It is important to understand that most of the RS-232C lines are

directional, that is, the protocol specifies which direction the signal

travels on each line, relative to the ends of the cable. Therefore, the
protocol specifies that at one end of an RS-232C cable there must be a

device of the type called "Data Communications Equi?ffient", or "DCE

1

'

for

short, and at the other end there must be a device of the type "Data

Terminal Equifffient,or "OTE" for short. The direction of the signal on a

given line can be determined once you decide which end of your cable has

which kind of device.

The tenus Data Communication Equipment and Data Tenuinal Equipment derive

from the original purpose for RS-232C - to connect a terminal with a

communication device such as a modem. A computer does not have to be

involved at all. Since a computer can either play the part of a terminal,
when connected to a modem, or it can play the part of communication
equipment, when connected to a terminal, a computer serial channel can be

used either as DeE or DTE. However, a given serial channel can only be
wired up as one or the other at anyone time. If the channel happens to be
wired up to look like CCE, and you want to connect it to another CCE such as
a rrodem, then the RS-232C connection will not wo rk. Both ends would be

transmi tting on the same lines and receiving on the same lines. Before tI1e

RS-232C connection can be made, in this case, you must rewire the computer's

serial channel so that it receives and transnits on the lines specified for

I1I'E.

The Bitstreamer II Board is shipped with one RS-232C Serial I/O Cable.

To enable one of the serial channels to communicate over an RS-232C line,

you will connect one end of this line to one of the three serial channel
sockets on the board, and the other end, having an RS-232C standard DB-25

female connector, to the back panel of the computer. The cable is designed

so that appropriate signals from the board are directed to the RS-232C lines

at the D8-25 connector as if it were Data Communications Equipment. Thus,

the resulting 08-25 socket at the rear of the computer is a DCE RS-232C

~. channel.

I

Additional 8itstreamer II Serial I/O Cables are available from Vector

Graphic for the second and third serial channels on the board.

Drivers are provided for each serial channel to enable the 8251 Transmit

Data and Receive Data lines to input or output at RS-232C voltage levels.

These receivers and drivers are already connected on the board, requiring no

jumpering. When a serial I/O cable is installed for a given serial channel,
these signals are connected to RS-232C lines 3 and 2 respectively.

In addition, for each of the 825l's, three of ~~e RS-232C control lines

are pulled up to +12V (lines 5,

6,

and 8). This is the ON state in RS-232C.

(Normally, this will ENABLE equipment that requires such a signal.) When a

serial I/O cable is installed for a given channel, these signals are

available on the cable's 06-25. These signals are always ON if the board is

used without modification. However, you can install jumpers and RS-232C
line drivers to enable the 8251 to dynamically control any t'NO of them via
software.