HT9580 datasheet(32/63 Pages) HOLTEK

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HT9580

April 28, 2000

Preliminary

The POCSAG paging code

A transmission using the ²CCIR Radio paging

Code No.1² (POCSAG code) is generated in ac-

cordance with the following rules (see the fol-

lowing Figure).

PR EA M B L E

BA T C H 1BA T C H 2

L A S T B AT C H

10 10 . .... ....1 0 10 10 10 1 0

F R AM E0

F R AM E1F R AM E7

18 A ddr es s B i t s

A d d r es s co d e w o r d

M essag e co d e w o r d

Bi t N u m b e r

2 t o 19

20/ 2 1

22 t o 3 1

31 I dl e c ode B i t pat t e r n

Id l e c o d e w o r d

31 S y n c h c o de B i t pat t e r n

S y n c h c o d e w o r d

10 C R C bi t s

20 M es s a g e B i t s

Sy n c h

C W

2 F unc t i on

Bi t s

10 C R C bi t s

POCSAG code structure

The transmission is started by sending a pre-

amble, consisting of at least 576 continuously

alternating bits (10101010...). The preamble is

followed by an arbitrary number of batch

blocks. Only complete batches are transmitted.

Each batch comprises 17 code-words of 32 bits

each. The first code-word is a synchronization

code-word with fixed pattern. The sync word is

followed by 8 frames (0~7) of 2 code-words each,

containing message information. A code-word

in a frame can either be an address, message or

idle code-word.

Idle code-words also have fixed patterns and

are used to fill empty frames or separate mes-

sages.

Address code-words are identified by an MSB of

logic 0 and are coded as shown in the POCSAG

code structure figure. A user address or RIC

(Receiver Identity Code) consists of 21 bits.

Only the upper 18 bits are encoded in the ad-

dress code-word (bits 2 to 19). The lower 3 bits

designate the frame number in which the ad-

dress is transmitted.

Four different call types can be distinguished

on each user address. The call type is deter-

mined by two functional bits in the address

code-word (bits 20 and 21). The POCSAG stan-

dard recommends the use (in Taiwan) of combi-

nations of data formats and function bits, as

shown in the following table. Other combina-

tions will be set by SPF16~SPF19.

Bit 20 (MSB)

Bit 21 (LSB)

Call Type

Data Format

Numeric

4-bit package

Alert only

Alpha-numeric

7-bit package

Data formats and function bits

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