SM8213 datasheet(10/33 Pages) NPC

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SM8213AM

NIPPON PRECISION CIRCUITS—10

Battery Saving (BS1, BS2, BS3)

The SM8213AM controls the intermittent-duty oper-

ation of the RF stage, which reduces battery con-

sumption, and three output 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 (61 steps). The maximum setup time

is 25.417 ms at 2400 bps, 50.833 ms at 1200 bps,

and 119.141 ms at 512 bps. Note that 3EH and

3FH are invalid settings for BS1.

BS2 (RF DC-level adjustment signal)—BS2 is

used to control the discharge of the receive signal

DC-cut capacitor. The function of BS2 is deter-

mined 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 (idle mode). In pream-

ble and 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 idle

mode signal receive timing. In preamble mode,

it stays LOW.

BS3 (PLL setup 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 (61 steps). The maximum setup time

is 25.833 ms at 2400 bps, 51.667 ms at 1200 bps,

and 121.094 ms at 512 bps. Note that 3FH is an

invalid setting for BS3.

Note that the setup times should be set up such that

(BS3 rising-edge setup time) > (BS1 rising-edge

setup time).

Figure 3. BS1, BS2 and BS3 timing (Lock mode, frame 3)

456

Self address

1.953*Nms (0.833*Nms)

[0.417*Nms]

1.953*Mms

(0.833*Mms) [0.417*Mms]

1.953*Nms (0.833*Nms)

[0.417*Nms]

1.953*Mms

(0.833*Mms) [0.417*Mms]

BREAK detection to reception stop (32 bit max.)

Receive code

BS1

BREAK command

BS2

(flag BS2 option = 0)

BS2

(flag BS2 option = 1)

BS3

Receive code

BS1

BS2

(flag BS2 option = 0)

BS2

(flag BS2 option = 1)

BS3

Address does not match

Self address

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