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Vector

Graphic Bitstrea.mertI~Boara

It is important to note here that in the RS-232C protocol, any given line

has

one

name,

regardless

of your

point

of view.

For example, although a

modern, which is a kind of

Data

Communications

Equipment

(llDCE"),

receives

its data

on line

2, line

2 is still called Transmitted Data.

Notice that

the names of the lines are more

meaningful

if you

look

at them

from

the

point

of view

of a tenninal at the other end of t..'1e

line, that is from t..~e

point of view of the Data Terminal Equir:ment (

It

DTE

It).

.~ccording to RS-232C,

Data Terminal

Equipment transmits on the Transmitted Data line and receives

on the Received Data line.

The

Bitstreamer

II

board

is wired

to

behave

as if it were

Data

Communications Equipment.

This

is reasonable

because

the board

is most

commonly

connected

to printers,

CRT's,

and other

kinds of Data Tenninal

Equipment.

This

explains

why

RS-232C

line

2 - Transmitted

Data

-

is

connected

to tha 8251

RxD

(Receive

Data)

line, and why line 3 - Received

Data - is connected to ~he 8251 TxD

(Transmit

Data)

line,

in the

factory

configuration.

If you want to connect the board to a rrodem, that is, you want the board

to behave

like Data

Terminal

Equipment, you have to reverse lines 2 and 3

somewhere.

The result would be that RS-232C Transmitted Data

is connected

to the 8251 TxD

pin and RS-232C Received Data is connected to the 8251 RxD

pin, which is exactly the way Data Terminal Equir:ment should behave.

To make

the board

look

like Data Terminal

Equipment,

you also should

eliminate

the +12

VDC

signals

on

lines

5,

6,

and

8,

unless

you

are

absolutely sure tl1at the Data Communications Equipnent you are connecting to

does not send handshaking signals on one or mora of these lines.

(Many low

speed

acoustic couplers do not use these lines.)

The reason is that if t..'1e

Data Communications Equipment has an RS-232C line driver connected to one of

these lines, the +12 VDC could blow it out.

To send handshaking signals:

Data Communication Equipment

connected

to

the board

may

requi ra a +12 VDC

on some other line (most often line 4 or

line 20).

Similarly, a piece of Data Terminal

Equipment

connected

to the

board may r12 VDC on some line other t..'1an

5, 6, or 8, though this is

rare.

You can 12 VDC as a constant enabling signal,

by connecting

the desired RS-232C line

(5)

to +12 VDC through a pull-up resistor.

Alternately, you can connect the required

line(s)

via an RS-232C

line

driver

to the 8251

and

thus allo\'lyour

software

to control

the +12 VDC

enabling

signal(s),

if desired.

The

8251

has

two

pins

that

can

be

controlled

by software.

They are pin 23 (RrS) and pin 24 (DTR).

Soft\vare

controls the status of these f'ins

by

outputtifB a command

instruction

byte

to

tha

8251,

as

described

in

the

8251

references

mentioned

in the

Perspective section of this manual.

Note that by sending a binary 1 to one

of these

status

lines,

the line

is turned

ON, which

is converted by t..'1e

RS-232C line driver into +12 VDC.

To receive handshaking signals:

Data CorrumunicationsEquipment connected

to ~he board may send +12 vTIChandshaking signals on one or more lines, most

often

RS-232C

lines

5, 6, 8 and/or 22,

Similarly, Data Tenninal Equipment

Summary of Contents for Bitstreamer II

Page 1: ...lit t tiCAli1iC I JI U E I mAnUAL...

Page 2: ......

Page 3: ...BITSTREAMER II BOARD Revision 1 USER S MANUAL Revision A January 1 1980...

Page 4: ...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 MANUA...

Page 5: ...o 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 cha...

Page 6: ......

Page 7: ...ic 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 WHAT the board does and requi res only a rooderate kn...

Page 8: ......

Page 9: ...rally 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 Rea...

Page 10: ...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 t...

Page 11: ...y 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 lin...

Page 12: ...s provided None prewired Output to parallel channel A selects masks interrupt sources previously wired in Dummy input from Parallel Channel a resets 55 Hz real t e clock interrupt line during an inter...

Page 13: ...ee 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...

Page 14: ...u 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 Finall...

Page 15: ...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 int...

Page 16: ...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 R...

Page 17: ...n 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 R...

Page 18: ......

Page 19: ......

Page 20: ...applications no additional RS 232C lines will be required other than those already connected to active components on the Bitstreamer II board connected either to drivers receivers or 12V Thus the seri...

Page 21: ...d the real time clock latch which becomes active and stays active as soon as it receives a pulse from the clock The output of this latch can then be connected to the interrupt line along with or inste...

Page 22: ...d no matter what the interrupt source on the board However if there are more than one aitstreamer II Boards in the system each of them can be wired to generate a different byte Therefore software can...

Page 23: ...accomplished using IN and OlJI machine language instructions within sof twa re prepared for specific applications Output is latched on the board so that after an OUT instruction is executed the eight...

Page 24: ......

Page 25: ...ght allowed base addresses 02 12 22 32 42 52 62 and 72 It should be clear that the left hand digit of the base address will be the same as the left hand digit of each of the board s I O addresses For...

Page 26: ...as the same function as address 47 on a Bitstreamer II board having base address of 42 The following table gives the function of each I O address I O address Example Name of Channel Connector on the B...

Page 27: ...are not using a particular serial channel do not worry about the position of its baud rate switch The labeled baud rates assume that the corresponding 8251 will be initialized for a clock factor of 1...

Page 28: ...rder to operate If you are not sure whether the board will work without modification try it before attempting to add additional handshaking signals Generally to IMke sure that you are connecting all t...

Page 29: ...400 Video Display Terminal Reference Manual May 1978 in Section 5 5 which direct you to cross lines 2 and 3 if connecting directly to a computer That instruction ass s you are connecting to a computer...

Page 30: ...eBitstreamer II Serial I O cable you have to string a wire from the RS 232C connector to the Bitstreamer II board Connect this line to t lle input of the spare RS 232C line receiver U26 pin 1 and conn...

Page 31: ...hree line cable with male D8 25 connectors at both ends Wire line 7 straight across and cross lines 2 and 3 In other words connect pin 2 of one connector to pin 3 of the other and vica versa Such a ca...

Page 32: ...s pin number on the l6 pin socket connected to the end of the Bitstreamer II Serial I O cable The table also lists those lines which are connected to components or jumper pads in the factory configur...

Page 33: ...Detector OCE 8 9 H I J 4 12 Reserved for Data Set Testing 9 Reserved for Da ta Set Testing 10 Unassigned 11 Secondary Received Line Signal Det OCE 12 Secondary Clear to Send OCE 13 secondarj Transmit...

Page 34: ...nal Equipment you also should eliminate the 12 VDC signals on lines 5 6 and 8 unless you are absolutely sure tl1atthe Data Communications Equipnent you are connecting to does not send handshaking sign...

Page 35: ...a re can tell that the 8251 is ready to transmit by monitoring the TxRDY bit in the status byte or by being interrupted by the TxRDY 8251 output pin 15 For information on the 8251 status byte refer to...

Page 36: ...each end The pairs of lines which are crossed are 2 and 3 4 and 5 6 and 20 and 8 and 19 All other lines are wired straight through If you are connecting an RS 232C handshaking line to some point on t...

Page 37: ...1489 receiver circuit to one of the 8251 input pins using one of the pads in Area N 0 or Pl 1488 a quad line driver 1489 a quad line receiver There is one spare receiver circuit and one spare driver...

Page 38: ...s simultaneously Connect the pads requiring voltage and ground to the voltage and ground jumper areas on the board found just below Areas E and F 12 vr c Input circuit A Output circuit A Input circuit...

Page 39: ...explained later Interrupt Source Pad in Area A Mask Bit Serial ChanneI A TxRDY 3 0 Serial Channel A RxRDY 6 1 Serial Channe1 B T RDY 7 2 Serial Channel B RxRDY 4 3 Serial Channe1 C TxRDY 2 4 Serial C...

Page 40: ...ts you output a byte to Parallel Channel A which is I O address x8 usually 08 This is the inter rupt masking re9iste r The cho ice of enabled and disabled lines remains the same until the next time yo...

Page 41: ...memory To accomplish this software must be set up as follows There must be a table of 16 bit startir 3 addresses for every interrupt service routine Each address in this table has to be arranged with...

Page 42: ...These pads are connected to the data bus Thus if L l is low it will pull one of the data bus lines low The resulting byte generated on the data bus is given in the table below Byte on Data Bus L l is...

Page 43: ...clock interrupt latch software must input from Parallel Channel 3 If a spurious interrupt is received for which software cannot determine a source it is a good idea to clear all potential interrupt u...

Page 44: ...even pin nlli bers in the back The connector cable is set up so that the lines are numbered 1 to 34 from left to right e functional definition of each line is as follows J4 J5 pin Function J4 J5 Pin...

Page 45: ...r NN D gates in chip U10 All the pins for L ese gates are accessible in jumper area 8 Each of these gates can be used as an inverter sim lyby tying the input to both of the input pins Note L at e outp...

Page 46: ......

Page 47: ...0 baud is generated by dividing the frequency for 2430 baud by 22 The desired frequency is selected by a DIP switch for each serial channel and applied to the TxC and RxC pins of the 8251 The 8251 U8A...

Page 48: ...o a specific bit in the output side of Parallel Channel A in order for b1 e corresp ndirl3 TxRDY or RxRDY to emerge inverted on the other side of the NAND gate Open collector gates are used so that th...

Page 49: ...000 0 Y Shl J 0 1 2 t I 0 0 s n o 10 I II On 6 ol r II I 0 52 lO l J I u Lol 52 l 1 5 O U Shl t 3 5 Sn tl I a 1 I I 1S l I 5 s H 1 I i O US1 I in o o 2 Qo z...

Page 50: ......

Page 51: ...no at all Just below area K VIO should read VI instead Notel 1atthe numbers 00101 the bus connectors shovV 1 be1 0 area K corresfX nd to the names of the VI lines in the S 100 bus and they are correct...

Page 52: ......

Page 53: ......

Page 54: ......

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