SM8213AM

NIPPON PRECISION CIRCUITS—8

Code words (address and message signals)

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

Call number to call sign conversion

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

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.

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

2

3456

7

1234

56

789 10 11 12 13 14 15 16 17 18 19 20 21

MSB

LSB

7 - digit decimal call signal (gap code) (8 to 2000000)

21 - bit binary conversion

Call sign

0

1

2

19

20

21

32

31

22

Frame

identification

pattern

Even - parity bit

(for bits 1 to 31)

BCH(31, 21) generated check bits

Flag : "0" = Adderss signal

Function bits

Bits 2 to 19 (18 bits)

Bits 22 to 31 (10 bits)

P