SM8211 데이터 시트보기 (PDF) - Nippon Precision Circuits

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SM8211

POCSAG Decoder For Pagers

Nippon Precision Circuits  

SM8211M

Operating Modes

The SM8211M has four operating modes—Switch-

ON, Preamble, Idle and Lock modes. Note that all

values in parentheses in the following figures are for

the case when the speed is 1200 bps.

Switch-ON mode

After power is applied and after RST has gone LOW

to reset all internal circuits, code words for the 27-bit

flag data and the six 18-bit addresses are received

from the CPU on TX-DATA and are stored. As each

code word comprises 32 bits, this process takes (32 ×

7) + 1 TX-CLK cycles to complete. When the 225

TX-CLK cycles have been received, BS1, BS2 and

BS3 are set and device operation transfers to pream-

ble mode.

RST

1 to 200 ms

X

TX-CLK

1

2

224

225

TX-DATA

127 ms (54.2 ms)

BS1

BS2

(BS2 flag = 0)

1.953 x N ms

(0.833 x N ms)

BS2

(BS2 flag = 1)

BS3

1.953 x M ms

(0.833 x M ms)

Preamble mode

X > 2 ms for external system clock operation or during continuous oscillations

X > 900 ms for internal oscillator operation immediately after power is applied or BACKUP is released (VDD = 1.5 to 3.5 V)

X > 1.5 s for internal oscillator operation immediately after power is applied or BACKUP is released (VDD < 1.5 V)

Figure 3. Switch-ON mode timing

NIPPON PRECISION CIRCUITS—8

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