PCD5008 datasheet(49/64 Pages) PHILIPS

49 / 64 page

1998 Jun 17

Philips Semiconductors

Product speciﬁcation

FLEX

™ Pager Decoder

PCD5008

8.8.3

ALL FRAME MODE (ID = 03H)

The FLEX

™ protocol requires pagers to be capable of

receiving data in frames other than pagers’ programmed

frames and frames implied by collapse values. This is

achieved in the PCD5008 by all frame mode (AFM) which

is required to implement the following features:

• Fragmented messages Section 8.8.5)

• Temporary addresses (Section 8.8.4).

The PCD5008 enters AFM automatically and when

in AFM, it decodes every FLEX

™ frame irrespective of

whether it is a programmed frame. In AFM the PCD5008

sends a status packet with the end-of-frame (EOF) bit set

at the end of every frame. In addition the host can force

AFM by sending an AFM packet with the force all frame

mode (FAF) bit set.

The PCD5008 contains a number of counters which are

used to track the number of active calls requiring AFM.

These consist of an AFM counter for tracking the number

of active fragmented messages and 16 temporary address

enable (TAE) counters which count the number of times

each temporary address has been enabled. These

counters are automatically incremented when a

corresponding vector is received, i.e.:

• A short instruction vector indicating a temporary address

has been assigned to this pager

• A vector indicating a message for this pager with a

format which allows fragmentation.

The host must determine when no further data can be

received for a message associated with a temporary

address, or a fragmented message, and send an

AFM packet, see Table 56, to decrement the appropriate

counter. AFM remains active until the host determines that

no further data can be sent to it outside programmed

frames, i.e:

• The TAE counters are all zero indicating that no further

temporary message data is expected

• The AFM counter is zero indicating that no further data

is expected for fragmented messages

• The FAF bit is clear.

Both the AFM counter and the TAE counters can only be

incremented internally by the PCD5008 and can only be

decremented by the host via AFM packet. Neither the

TAE counters nor the AFM counter can be incremented

past the value 127 (it does not roll-over) or decremented

past the value 0. The TAE counters and the AFM counter

are cleared on a reset and when the decoder is turned off.

DAF: decrement all frame mode counter, see Table 56.

Setting this bit decrements the AFM counter by one. If a

packet is sent with this bit clear, the AFM counter is not

affected. Value after reset = 0.

FAF: force all frame mode, see Table 56. Setting this bit

forces the PCD5008 to enter AFM. If this bit is clear, the

PCD5008 may or may not be in AFM depending on the

status of the AFM counter and the TAE counters. This

functionality may be useful in acquiring transmitted time

information. Value after reset = 0.

DTA: decrement temporary address enable counter, see

Table 56. When a bit in this word is set, the corresponding

TAE counter is decremented by one. When a bit is clear,

the corresponding TAE counter is not affected. When a

TAE counter reaches zero, the temporary address is

disabled. Value after reset = 0.

Table 56 All frame mode packet bit assignments

BYTE

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

300000011

DAF

FAF

000000

1DTA15

DTA14

DTA13

DTA12

DTA11

DTA10

DTA9

DTA8

0DTA7

DTA6

DTA5

DTA4

DTA3

DTA2

DTA1

DTA0

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