SM8211M

NIPPON PRECISION CIRCUITS—6

Code words (address and message signals)

Each code word comprises 32 bits as shown in table 2.

Call number to call sign conversion

1. The MSB is the address/message code word control bit. It is 0 for an address signal, and 1 for a message signal.

2. Bits 2 to 21 contain the address or message information.

3. Bits 22 to 31 are BCH(31,21) format generated check bits, where BCH(n,k) = BCH(word length, number of information bits).

4. The LSB is an even-parity bit for bits 1 to 31.

This conversion expands a 7-digit decimal call num-

ber into a 21-bit binary call sign, as shown in figure

2.

After expansion, the high-order 18 bits are assigned

to bits 2 to 19 (address signal), and the low-order 3

bits are the user-defined frame identification pattern,

which is stored in ID-ROM. The two function bits

define which of four call functions is active.

Table 2. Code word format

Code word

Bit number

Address signal

0

Address bits

Function bits

Check bits

Even-parity bit

Message signal

1

Message bits

Check bits

Even-parity bit

20

21

Function

0

0

A call

0

1

B call

1

0

C call

1

1

D call

Figure 2. Call number to call sign conversion

1

7-digit decimal call

signal (gap code)

Bits 2 to 19 (18 bits)

2

3

4

5

6

7

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

20

21

32

1

Bits 22 to 31 (10 bits)

MSB

LSB

21-bit binary

conversion

Call sign

Frame

identificaton

pattern

Function bits

BCH(31,21) generated check bits

Flag:

0 = address signal

1 = message signal

Even-parity bit

(for bits 1 to 31)