SM8211M datasheet(7/22 Pages) NPC

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SM8211M

NIPPON PRECISION CIRCUITS—7

Idle signal (dummy signal)

An idle word can be inserted into either the address

or message signal to indicate that the word contains

no information. The idle word bit pattern is shown in

table 3. Message reception is halted when the

receiver detects an idle word.

In pager systems that send numeric data, the number

of frames varies with the type of message being sent.

In this case, an idle signal is transmitted to indicate

completion of the message.

Receive signal duty factor

During preamble detection, the preamble pattern

(1,0) is recognized at duty factors from 25% (min) to

75% (max) of the (1,0) preamble cycle.

Battery Saving (BS1, BS2, BS3)

The SM8211M controls the intermittent-duty opera-

tion of the RF stage, which reduces battery consump-

tion, and outputs three control signals (BS1, BS2,

BS3). The function each signal controls in each

mode is described below.

BS1 (RF-control main output signal)—The RF

stage is active when BS1 is HIGH. The rising-

edge setup time for receive timing is set by ﬂags

RF0 to RF5 (60 steps). The maximum setup time

is 49.167 ms at 1200 bps, and 115.234 ms at 512

bps.

Note that 3C, 3D, 3E and 3F are invalid settings

for BS1.

BS2 (RF-control output signal)—BS2 is used to

control the discharge of the receive signal DC-cut

capacitor. The function of BS2 is determined by

ﬂag BS2, as described below.

• When ﬂag BS2 is 0, pin BS2 goes HIGH

together with BS1 and then goes LOW again

after the BS1 setup time. However, in lock

mode (during address/message reception), it

stays LOW.

• When ﬂag BS2 is 1, pin BS2 goes HIGH during

lock mode sync code receive timing, and pre-

amble mode and idle mode signal receive tim-

ing.

BS3 (RF-control output signal)—BS3 is used to

control PLL operation when the PLL is used. The

rising-edge setup time for receive timing is set by

ﬂags PL0 to PL5 (60 steps). The maximum setup

time is 50.833 ms at 1200 bps, and 119.141 ms at

512 bps.

Note that 3E and 3F are invalid settings for BS3.

Note also that (BS3 rising-edge setup time)

− (BS1

rising-edge setup time) should be

≥ 2.

Table 3. Idle code word

Bit

number

Bit value

Bit

number

Bit value

100260

110270

120281

131290

140301

150311

161321

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