PCF5001T データシートの表示（PDF） - Philips Electronics

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PCF5001T

POCSAG Paging Decoder

Philips Electronics 

Philips Semiconductors

POCSAG Paging Decoder

Product specification

PCF5001

7.3 Modes and states of the decoder

The PCF5001 supports two basic operating modes:

• ‘Alert-only pager’ mode

• ‘Display pager’ mode.

Two further modes, the programming mode and the test

mode, are implemented to program and verify the

EEPROM contents and to support pager production and

approval tests, respectively.

In ‘alert-only pager’ mode no external microcontroller is

required, see Fig.22. A three position slider switch

interface is provided to select the internal state of the

decoder. The decoder performs regular scanning of the

switch inputs to detect a status change. A push-button

interface is provided on the SR input, which is used as

input for user acknowledgment actions and status

interrogation. Upon reception of valid calls, tone alert

cadences are generated. A call storage is provided to store

calls received while operating in SILENT status and to

recall cadences upon ‘repeat’ mode operation.

The voltage doubler and the frequency reference output

are disabled in this mode.

In ‘display pager’ mode the PCF5001 operates as decoder

and pager controller in combination with an external

microcontroller (see Fig.23). The internal states of the

decoder are determined by appropriate logic levels on the

status inputs. A bus type interface structure is used to

interface the decoder to the microcontroller. The decoder's

on-chip voltage converter provides doubled supply voltage

output to provide a higher supply voltage to the

microcontroller and any additional hardware. The logic

levels of the interface's input and output signals are level

shifted to allow for direct coupling between microcontroller

and the decoder. Upon detection of a valid call, address

and message information are transferred to the external

microcontroller using the serial microcontroller interface.

In addition, appropriate call alert cadences are generated.

If the decoder is in one of the two operating modes, it is

always in one of the following three internal states:

• OFF status. This is the power saving, inactive status of

the PCF5001. The paging receiver is disabled, no

decoding of input data takes place. However, the crystal

oscillator is kept running to ensure that scanning of the

status inputs/status switch is maintained to allow

changing into one of the following two active states.

• ON status. This is the normal active status of the

decoder. Incoming calls are compared with the user

addresses stored in the internal EEPROM. Upon

detection of valid calls, alert cadences and LED

indication are generated and data is shifted out at the

serial microcontroller interface.

• SILENT status. The SILENT status is the same as the

ON status with the exception that valid calls no longer

cause generation of call alert cadences. Instead, if

programmed as ‘alert-only pager’, the decoder stores up

to eight different calls and generates appropriate alert

cadences after the decoder has been put back into the

ON status. However, special SILENT override calls will

cause generation of alert cadences, if enabled.

The decoder operating status is selected as indicated in

Table 1.

When programmed for ‘alert-only pager’ a switch

debounce period is applied to the status inputs. For status

change and status interrogation in ‘display pager’ mode,

see Figs 6 and 7.

Table 1 Truth table for decoder operating status

ON INPUT

0

0

1

1

SK INPUT

0

1

0

1

OPERATING STATUS

OFF

OFF (EEPROM transfer mode; note 1)

ON

SILENT

Note

1. The EEPROM transfer mode applies to ‘display pager’ mode only.

1997 Mar 04

11

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