MICRF221 datasheet(18/26 Pages) MICREL

18 / 26 page

Micrel Inc.

MICRF221

October 2008

M9999-100108

(408) 955-1690

T1 < 0.1 us, Time from SCLK to convert DO to input

T6 > 0.1 us, SCLK high time

T7 > 0.1 us, SCLK low time

T2, T3, T4, T5, T8, T9, T10 > 0.1 us

DO PIN AS OUTPUT

“1”

“0”

“1”

SCLK

T10

BIT TIME 18

BIT TIME 19

Figure 14. Serial Interface Stop Sequence

Serial Interface Examples

All bits (D19 through D0) low (channel 1 is the DO pin,

and Channel 2 is the SCLK pin), see Figure 15.

Figure 15. All bits 0s.

All bits (D19 through D0) High, Figure 16.

Figure 16 All bits 1s.

Only bits 19 and 18 High, Figure 17.

Figure 17 D19 = D18 = 1.

Autopoll example, Figure 18.

D0 = D1 = D2 = 0, no desense

D3 = D4 = 0, demodulator bandwidth = 1712 hertz, 1

kHz baud rate, pulse = 500 usec, required

demodulator bandwidth is 0.65/500usec = 1300 hertz

D5 = D6 = 1, Slice level = 50%

D7 = 0, D8 = 1, bit check = 4 bits. This is the time the

device is ON checking for four consecutive valid

windows.

D9 = D10 = 1, D11 = 0, data rate is 1 kHz, (500 usec

pulses), window set to 433 usec (< 500 usec)

D12 = D13 = 0, D14 = 1, sleep timer set to 160 msec,

that is, 4 bit is ON and 160 msec is OFF.

D15 = 1, device is placed in autopoll

D16 = 0, normal demodulator bandwidth

D17 = 0, squelch is OFF

D18 = 1, watchdog timer is OFF

D19 = 0, no RSSI offset

From MSB to LSB, see Table 7:

D19

D18

D17

D16

D15

D14

D13

D12

D11 D10 D9

Table 7. Autopoll example bit sequence

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