background image

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 bronediate relevence 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 (about

a

Vdc) 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

speci

f

ies

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.

Содержание Bitstreamer II

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

Страница 2: ......

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

Страница 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...

Страница 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...

Страница 6: ......

Страница 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...

Страница 8: ......

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 18: ......

Страница 19: ......

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 24: ......

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 46: ......

Страница 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...

Страница 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...

Страница 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...

Страница 50: ......

Страница 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...

Страница 52: ......

Страница 53: ......

Страница 54: ......

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