MICRF229 datasheet(14/23 Pages) MICREL

14 / 23 page

Micrel, Inc.

MICRF229

April 15, 2015

Revision 1.0

The auto-polling feature is noise sensitive in that if the

noise level is sufficiently high, the MICRF229 could be

awaken in the absence of valid RF signal due to its

internal noise. To ensure that the device only wakes up

upon the reception of valid data, increase the number of

valid bits in the bit check register D[8:7] setting. The

recommend setting is 11.

Table 6. Sleep Timer Control

D14

D13

D12

Set Sleep Time

10ms

20ms

40ms Default

80ms

160ms

320ms

640ms

1280ms

Table 7. Sleep Auto-Poll Control

D15

Auto-Poll Enable

Awake – does not poll - default

Auto-polls with sleep periods

Table 8. Sleep Auto-Poll Control for 433.92MH

D11

D10

Set Bit-Check Window Time

(433.92MHz, Time In

μs)

D4 = 1

D3 = 1

D4 = 1

D3 = 0

D4 = 0

D3 = 1

D4 = 0

D3 = 0

143

285

570

133

266

532

124

247

494

114

228

457

105

209

419

190

381

172

343

152

305

Note:

Default value of D{11:9} = 111.

Table 9. Number of Valid Bit Control

Set Number of Consecutive Valid

Bits Before Releasing DO

Bitcheck 0 bits - default

Bitcheck 2 bits

Bitcheck 4 bits

Bitcheck 8 bits

Serial Interface Register Programming

There are twenty register bits in the MICRF229. Bits D15

− D19 have specific set points:

• D15: Default = 0; set to 1 only when auto-poll is in use.

• D16: Default = 0; set to 1 only when high bandwidth is

in use.

• D17: Default = 0 for normal operation.

• D18: This bit must always be set to 1.

• D19: For normal application, always set this bit to 0.

All other register bits must be set according to the

specific application as detailed in the previous sections.

Programming the device is accomplished by the use of

DO and SCLK. Normally, DO is outputting data and

needs to switch to an input pin made by the start

sequence, as shown at Figure 7.

High at the SCLK pin tri-states the DO pin, enabling the

external drive into the DO pin with an initial low level. The

start sequence is completed by taking SCLK low, then

high while DO is low, followed by taking DO high, then

low while SCLK is high. The serial interface is initialized

and ready to receive the programming data.

SCLK frequency should be greater than 5kHz to avoid

automatic reset from internal circuitry.

Figure 7. Serial Interface Start Sequence

MICRF229 Datasheet(PDF) 14 Page - Micrel Semiconductor

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