MICRF229 datasheet(15/23 Pages) MICREL

15 / 23 page

Micrel, Inc.

MICRF229

April 15, 2015

Revision 1.0

Bits are serially programmed starting with the most

significant bit (MSB = D19) if all bits are being

programmed until the least significant bit (LSB = D0). For

instance, if only the bits D0, D1, and D2 are being

programmed, then these are the only bits that need to be

programmed with the start sequence, D2, D1, D0, plus

the stop sequence. Or, if only the bit D17 is needed, then

the sequence must be from start sequence, D17 through

D0 plus the stop sequence, making sure the other bits

(besides

D17)

are

programmed

needed.

recommended that all parallel input pins (SEL0 and

SEL1) be kept high when using the serial interface.

After the programming bits are finished, a stop sequence

(as shown in Figure 8) is required to end the mode and

re-establish the DO pin as an output again. To do so, the

SCLK pin is kept high while the DO pin changes from low

to high, then low again, followed by the SCLK pin made

low. Timing of the programming bits are not critical, but

should be kept as shown below:

• T1 < 0.1µs, Time from SCLK to convert DO to input pin

• T6 > 0.1µs, SCLK high time

• T7 > 0.1µs, SCLK low time

• T2, T3, T4, T5, T8, T9, T10 > 0.1µs

Figure 8. Serial Interface Stop Sequence

Serial Interface Register Loading Examples

Channel 1 is the DO pin and Channel 2 is the SCLK pin.

Figure 9. All Bits D19 through D0 = 0

Figure 10. All Bits D19 through D0 = 1

Figure 11. D[19;18] = 11, D[17:0] = All 0s

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