intersil HD-15531 DATA SHEET

TM

HD-15531

March 1997

Features

• Support of MIL-STD-1553

• Data Rate (15531B) . . . . . . . . . . . . . . . .2.5 Megabit/Sec

• Data Rate (15531). . . . . . . . . . . . . . . . .1.25 Megabit/Sec

• Variable Frame Length to 32 Bits

• Sync Identification and Lock-In

• Separate Manchester II Encode, Decode

• Low Operating Power . . . . . . . . . . . . . . . . . 50mW at 5V

Ordering Information

PACKAGE

PDIP

CERDIP

DESC
(CERDIP)

TEMP. RANGE

(oC)

-40 to 85 -

-40 to 85

-55 to 125

-55 to 125

-55 to 125

1.25MBIT
/SEC

HD1-15531-9 HD1-15531B-9

HD1-15531-8 HD1-15531B-8

5962­9054901MQA

5962­9054902MQA

2.5MBIT
/SEC

HD3-15531B-9

HD1-15531

HD1-15531B

PKG.

NO.

E40.6

F40.6

F40.6

F40.6

F40.6

CMOS Manc hester Enc od er - D ec od er

Description

The Intersil HD-15531 is a high performance CMOS device
intended to service the requirements of MIL-STD-1553 and
similar Manchester II encoded, time division multiplexed
serial data protocols. This LSI chip is divided into two sec­tions, an Encoder and a Decoder. These sections operate
independentl y of each other, except for the master reset and
word length functions. This circuit provides many of the
requirements of MIL-STD-1553. The Encoder produces the
sync pulse and the parity bit as well as the encoding of the
data bits. The Decoder recog nizes the sync pul se and identi­fies it as well as decod ing the data bits and checking parity.

The HD-15531 also surpasses the requirements of MIL­STD-1553 by allowing the word length to be programmable
(from 2 to 28 data bits). A frame consists of three bits for
sync followed by the data word (2 to 28 data bits) followed by
one bit of parity, thus, the frame length will vary from 6 to 32
bit periods. This chip also allows selection of either even or
odd parity for the Encoder and Decoder separately.

This integrated circuit is fully guaranteed to support the
1MHz data rate of MIL-STD-1553 o ver both temperatu re and
voltage. For high speed applications the 15531B will support
a 2.5 Megabit/sec data rate.

The HD-15531 can also be used in many party line digital
data communications applications, such as a local area net­work or an environmental cont rol sys tem drive n from a single
twisted pair of fiber optic cable throughout a buil ding.

CAUTION: These devices are sen sitive to electr ostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143
Copyright © Intersil Americas Inc. 2002. All Rights Reserved

| Intersil (and design) is a trademark of Intersil Americas Inc.

1

FN2961.1

Pinout

V

VALID WORD

TAKE DATA’

TAKE DATA

SERIAL DATA OUT

SYNCHR DATA

SYNCHR DATA SEL

SYNCHR CLK

DECODER CLK
SYNCHR CLK SEL
BIPOLAR ZERO IN

BIPOLAR ONE IN

UNIPOLAR DATA IN

DECODER SHIFT CLK

TRANSITION SEL

NC

COMMAND SYNC

DECODER PARITY SEL

DECODER RESET

COUNT C

HD-15531

HD-15531 (CERDIP, PDIP)

TOP VIEW

1

CC

2
3
4
5
6
7
8

9
10
11
12
13
14
15
16
17
18
19
20

0

40
39
38
37
36
35
34

33
32
31
30
29
28
27
26
25
24
23
22
21

COUNT C

1

COUNT C

4

DATA SYNC
ENCODER CLK
COUNT C

3

NC
ENCODER SHIFT CLK

SEND CLK IN
SEND DATA
ENCODER PARITY SEL
SYNC SEL
ENCODER ENABLE
SERIAL DATA IN
BIPOLAR ONE OUT
OUTPUT INHIBIT
BIPOLAR ZERO OUT

÷ 6 OUT

COUNT C2
MASTER RESET
GND

Block Diagrams

GND

21

MASTER RESET

22

SEND CLK IN

33

÷ 6 OUT

24

ENCODER

37

CLK

BIT

COUNTER

20 40 23 36 39

C0C1C2C3C

÷ 6

ENDODER

V

CC

1

OUTPUT

INHIBIT

ENCODER

PARITY

SELECT

27

25

÷ 2

CHARACTER

FORMER

34 28 29 31

32

SEND
DATA

4

ENCODER

SHIFT

CLK

SERIAL

DATA IN

ENCODER

ENABLE

30
SYNC

SELECT

26

BIPOLAR
ONE OUT

BIPOLAR
ZERO OUT

2

HD-15531

DECODER

7 8

DATA

SELECT

GATE

CLOCK

SELECT

DATA

DECODER

RESET

DATADATA SELECT

CHARACTER

IDENTIFIER

BIT

RATE

CLK

19

20 40 23 36 39

C

BIT

COUNTER

0C1C2C3C4

PARITY
CHECK

4

17

5

2

16

14

3

UNIPOLAR

DATA IN

BIPOLAR

ONE IN

BIPOLAR

ONE IN

DECODER

CLK

DECODER

CLK SELECT

SYNCHRONOUS

SYNCHRONOUS

CLK

CLK SELECT

MASTER

RESET

SYNCHRONOUS SYNCHRONOUS

13

12

TRANSITION

FINDER

11

9

SYNCHRONIZER

15

8

10

22

Pin Description

PIN

NUMBER TYPE NAME SECTION DESCRIPTION

TAKE DATA
COMMAND SYNC

DATA SYNC
SERIAL

DATA OUT
VALID WORD

PARITY
SELECT

DECODER
SHIFT CLK

TAKE DATA’

1V

CC

Both Positi ve supp ly pi n. A 0 .1 µF decoupling capacitor from VCC (pin 1) to GROUND

(pin 21) is recommended.

2 O VALID WORD Decoder Output high indicates receipt of a valid word, (valid parity and no Manchester

errors).

3 O TAKE DATA’ Dec oder A continuous , fr ee ru nnin g si gnal prov ided for host timi ng o r d ata ha ndli ng. When

data is presen t on the bus, this signal will b e synchronized to the incoming data
and will be identical to TAKE DATA.

4 O TAKE DATA Decoder Output is high du rin g rec ei pt of data af ter id ent if ica t ion of a va l id syn c pu lse an d

two va li d Ma nc he ster bits.
5 O SERIAL DATA OUT Decoder Delivers received data in correct NRZ format.
6 I SYNCHRONOUS

DATA

Decoder Input presents Manchester data directly to character identification logic.

SYNCHRONOUS DATA SELECT must be held high to use this input. If not

used, this pin must be held high.
7 I SYNCHRONOUS

DATA SELECT

8 I SYNCHRONOUS

CLOCK

Decoder In high state allows the synchronous data to enter the character identification

logic. Tie this in put low for asynchronous data.

Decoder Input provide s externally synchronized clock to th e decoder, for use whe n re-

ceiving synchronous data. This input must be tied high when not in us e.
9 I DE CO DE R CLOCK Decoder Input drives t he tra ns it ion fi n de r, a nd the syn ch ron iz er whi ch i n tur n su ppli es t he

clock to the balance of the decoder. Input a frequency equal to 12X the data rate.

10 I SYNCHRONOUS

CLOCK SELCT

Decoder In high state directs the SYNCHRONOUS CLOCK to control the decoder char-

acter ide ntification logic. A low state selects the DECODER CLOCK.

11 I BIPOLAR ZERO IN Decoder A high input should be applied when the bus is in its negative state. This pin must

be held high when the unipolar input is used.

12 I BIPOLA R ONE IN Decoder A high input s ho ul d b e ap pl ie d whe n t h e bus i s i n i ts posi t iv e s ta te. T his pi n mus t

he held low when the unipolar input is used.

13 I UNIPOLAR DATA IN Decoder With pin 11 high and pin 12 low, this pin enters unipolar data into the tr ansition

finder circuit. If not used this input must be held low.

3

HD-15531

Pin Description (Continued)

PIN

NUMBER TYPE NAME SECTION DESCRIPTION

14 O DECODER SHIFT

CLOCK

15 I TRANSITION SE-

LECT

16 NC Blank Not connected.
17 O COMMA N D SYNC Decode r O utput of a high from this pin occur s dur in g ou tput of deco de d data whi ch was

18 I DECODER PARITY

SELECT

19 I DECODE R RESET Dec oder A high input to t hi s p in dur i ng a risi n g ed ge of DEC ODE R SHI F T CLOC K r es ets

20 I COUNT C0 Both One of f iv e b inar y i np uts w hi ch esta bl is h t he to ta l b it co un t to b e en co de d or de -

21 GROUND Both Su pply pin.
22 I MASTER RESET Both A hi gh on this pin clears 2:1 counters in both encoder and decoder, and resets

Decoder Output which delivers a frequency (DECOD ER CLOCK + 1 2), synchronous by

the recovered serial data stream.

Decoder A high input to this pin causes the transition finder to synchron ize on every tran -

sition of input da ta. A low i nput causes the transition finder to synchronize only

on mid-bit transitions.

preceded by a Comma nd (or Status) synchronizing charac ter.

Decoder An input for parity sense, calling for even parity with input high and odd parity

with input low.

the decoder bit counting logic to a cond ition ready for a new word.

coded.

the ÷ 6 circu it.

23 I COUNT C2 Both See pin 20.
24 O
25 O BIPOLAR

26 I OUTPUT
27 O BIPOLAR

28 I SERIAL DATA IN Encoder Accepts a serial data stream at a data rate equal to ENCODER SHIFT CLOCK.
29 I ENCODER ENABLE Encoder A high on this pin initiates the encode c ycle. (Subject to the preceding cycl e be-

30 I SYNC SELE CT Encoder Ac tuates a Command sync for an input high and Data sync for an input low.
31 I ENCODER PARITY

32 O SEND DATA Encoder Is an active high output which enables the external source of serial data.
33 I SEND CLOCK IN Encoder Clock in pu t at a f req ue ncy e qu al t o th e da ta rat e X2, u su al ly dri ve n by ÷ 6 ou tp ut .
34 O ENCODER SHIFT

35 NC Blank Not connected.
36 I COUNT C3 Both See pin 20.
37 I ENCODER CLOCK Encoder Input to the 6:1 divider, a frequency eq ual to 12 times the data rate is usually

38 O DATA SY NC Deco de r O u tput of a high fro m this pin occurs durin g ou tp ut of de co de d data whi ch was

39 I COUNT C4 Both See pin 20.
40 I COUNT C1 Both See pill 20.

÷ 6 OUT Encoder Output from 6:1 divider which is driven by the ENCODER CLOCK.

ZERO

OUT

INHIBIT Encoder A low on th is pin forc es pin 25 and 27 high , the inactive stat es.

ONE OUT Encoder An active lo w out p ut desi gn ed to dri ve t he one o r pos iti ve s en se o f a bi pola r li ne

SELECT

CLOCK

Encoder An active low output designed to drive the zero or negative sense of a bipolar

line driver.

driver.

ing complete).

Encoder Sets transmit parity odd for a high input, even for a low input.

Encoder Output for shifting data into the Encoder. The Encoder samples SDI pin-28 on

the low-to-high transition of ESC.

input here.

preceded by a data synchronizing character.

4

Encoder Operation

HD-15531

The Encoder requires a single clock with a frequency of
twice the desired data rate applied at the SEND CLOCK
input. An auxiliary divide by six counter is provided on chip
which can be utilized to produce the SEND CLOCK by divid­ing the DECODER CLOCK. The frame length is set by pro­gramming the COUNT inputs. Parity is selected by
programming ENCODER PARITY SELECT high for odd par­ity or low f o r even pa rity .

The Encoder’s cycle begins when ENCODER ENABLE is
high during a falling edge of ENCODER SHIFT CLOCK .
This cycle lasts for one word length or K + 4 ENCODER
SHIFT CLOCK periods, where K is the number of bits to be
sent. At the next low-to-high transition of the ENCODER
SHIFT CLOCK, a high SYNC SELECT input actuates a
Command sync or a low will produce a Data sync for the
word . When the Encoder is ready to accept data, the

2

SEND DATA output will go high for K ENCODER SHIFT
CLOCK periods . During these K periods the data should

TIMING 0 1 2 3 4 5 6 7 N-3 N-2 N-1 NN-4

SEND CLOCK

ENCODER

SHIFT CLOCK

ENCODER

ENABLE

SYNC

SELECT

SEND

DATA

4

DON’T CARE

VALID

DON’T CARE

be clocked into the SERIAL DATA input with every high-to­low transition of the ENCODER SHIFT CLOCK - so it
can be sampled on the low-to-high transition. After the sync
and Manchester II encoded data are transmitted through the
BIPOLAR
adds on an additional bit with the parity for that word . If
ENCODER ENABLE is held high continuously, consecutive
words will be encoded without an interframe gap.
ENCODER ENABLE must go low by time (as shown) to
prevent a consecutive word from being encoded . At any time

1

a low on OUTPUT
puts to a high state but will not affect the Encoder in any
other way.

To abort the Encoder transmission, a positive pulse must be
applied at MASTER RESET. Any time after or during this
pulse, a low-to-high transition on SEND CLOCK clears the
internal counters and initializes th e Encoder for a new word.

3 4

ONE and BIPOLAR ZERO outputs, the Encoder

5

5

INHIBIT input will force both bipolar out-

SERIAL

DATA IN

BIPOLAR
ONE OUT

BIPOLAR

ZERO OUT

1ST HALF 2ND HALF MSB BIT K-1 BIT K-2 BIT K-3 BIT K-4

SYNC SYNC MSB BIT K-1

BIT K-1 BIT K-3 BIT K-4 BIT K-5 BIT 4BIT K-2MSB BIT 3 BIT 2 BIT 1

BIT K-2 BIT K-3 BIT K-4

FIGURE 1. ENCODER

Decoder Operation

To operate the Decoder asynchronously requires a single
clock with a frequency of 12 times the desired data rate
applied at the DECODER CLOCK input. To operate the
Decoder synchronously requires a SYNCHRONOUS
CLOCK at a frequency 2 times the data rate which is syn­chronized with the data at every high-to-low transition
applied to the SYNCHRONOUS CLK input. The Manchester
II coded data can be presented to the Decoder asynchro­nously in one of two ways. The BIPOLAR ONE and
BIPOLAR ZERO inputs will accept data from a comparator
sensed transformer coupled bus as specified in Military Spec

1553. The UNIPOLAR DATA input can only accept nonin­verted Manchester II coded data. (e.g., from BIPOLAR

ONE

PARITYBIT 1BIT 2BIT 3BIT 4

BIT 4 BIT 3 BIT 2 BIT 1

PARITY

4 5321

OUT on an Encoder through an inverter to Unipolar Data
Input).

The Decoder is free running and continuously monitors its
data input lines for a valid sync character and two valid
Manchester data bits to start an output cycle. When a valid
sync is recognized , the type of sync i s indicated by a high

1

level at either COMMAND SYNC or DATA SYNC output. If
the sync character was a command sync the COMMAND
SYNC output will go high and remain high for K SHIFT
CLOCK periods , where K is the number of bits to be

3

2

received. If the sync character was a data sync, the DATA
SYNC output will go high. The TAKE DATA output will go
high and remain high - while the Decoder is transmit-

2 3

5