HT9580 datasheet(33/63 Pages) HOLTEK

33 / 63 page

HT9580

April 28, 2000

Preliminary

Alert-only calls consist of a single address

code-word. Numeric and alphanumeric calls

have message code-words following the address.

Message code-words are identified by an MSB

of logic 1. The message information is stored in

a 20-bit field (bits 2 to 21). The data format is

determined by the call type: 4 bits per digit for

numeric message and 7 bits per (ASCII) charac-

ter for alphanumeric messages. Each

code-word is protected against transmission er-

rors by 10 CRC check bits (bit 22 to 31) and an

even parity bit (bit 32).

This permits correction of a maximum of 2 ran-

dom errors or up to 4 errors in a burst of 4 bits

(a 4-bit burst error) per code-word.

· Error correction

Item

Description

Address

code-word

two random errors, or 4-bit

burst errors (optional)

Message

code-word

two random errors, or 4-bit

burst errors (optional)

Error correction

In the HT9580, error correction methods have

been implemented as shown in the table above.

Random error correction is the default for

both address and message code-word. In an-

other method, burst error correction can be

switched by SPF programming. Up to 4 erro-

neous bits in a 4-bit burst can be corrected.

The error type detected for each code-word is

identified in the message data output to the

microcontroller, allowing rejection of calls with

too many errors.

· Operating states

ON status

STANDBY status

The operating state is determined by control

address (0019H) bit 0 and monitored by bit 3

of address (0019H).

Truth table for decoder operating status

ON Input

Operating Status

On state

STANDBY state

· On status

In the ON status, the decoder pulses the re-

ceiver, quick charge and PLL enable outputs

(respectively BS1, BS2 and BS3) according to

the code structure and the synchronization

algorithm. Data received serially at the data

input (DI) is processed for call receipt.

· STB status

In the STB status the decoder will neither ac-

tivate the receiver, quick charge or PLL en-

able outputs, nor process any data at the data

input. The crystal oscillator remains active to

permit communication with the microcontrol-

ler.

· Battery saving

Current consumption is reduced by switching

the STB internal decoder sections whenever

the receiver is not enabled. To further increase

battery efficiency, reception and decoding of an

address code-word is stopped as soon as the un-

corrected address field differs by more than

3-bits from the enabled RICs. If the next

code-word has to be received again, the receiver

is re-enabled, thus observing the programmed

establishment times tBS1 ,tBS2 and tBS3.

· Data reception and buffer

Reception of a valid paging call is signaled to

the microcontroller by means of an interrupt

signal. The received address and message

code-word can then be read via a 46 bytes

message buffer (from 0040H to 006DH) for de-

coder data message. If the mC did not read the

previous message within one code-word time

from the message buffer, the message buffer

data will be overwritten.

· Bit rates

The HT9580 can be configured for data rates

of 512, 1200 or 2400 bit/s by SPF program-

ming. These data rates are derived from

32.768kHz, 76.8kHz or 153.6kHz oscillator

frequencies.

· Input data processing

The input data is noise filtered by means of a

digital filter. Data is sampled at 16 times the

data rate and averaged by majority decision.

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