MICRF405 datasheet(10/46 Pages) MICREL

10 / 46 page

Micrel

MICRF405

April 2006

M9999-041906

(408) 955-1690

SEN

SIO

SCK

Data to write

into register

Internal load pulse

generated here

A6 A5 A4 A3 A2 A1 A0 R/W D7 D6D5 D4 D3 D2 D1 D0

Figure 2. Writing to One Address.

In Figure 2, SIO is changed at positive edges of

SCK. The MICRF405 samples the SIO line at

negative edges. The value of the R/W bits is always

“0” for writing.

Writing to All Registers

Writing to all register can be done at any time. To

get the simplest firmware, always write to all

registers. The price to pay for the simplicity is

increased write-time, which leads to increased time

to change the way the MICRF405 works. If data is

transferred through DATAIN pin write address 0-23

(address 24-29 is don’t care). If data is transferred

through SPI write address 0-28 (Address 29 is only

written

during

data

transfer,

not

during

configuration).

What to write

Field

Comments

Address:

‘0000000’ (address of the first register to write to, which is 0)

R/W bit:

“0” for writing

Values:

st Octet: wanted values for ControlRegister0. 2nd Octet: wanted values for ControlRegister1 and

so on for all of the octets.

Table 5. When writing to All Registers, totally 25/30 (5 are optional) octets are clocked into the MICRF405.

How to write:

• Bring SEN low

• Use SCK and SIO to clock in the 25/30 octets

• Bring SEN high

Refer to Figure 3. Writing to n Registers Having

Incremental Addresses.

Writing to n Registers Having Incremental

Addresses

In addition to entering all bytes, it is also possible to

enter a set of n bytes, starting from address i = “A6,

A5, … A0”. Typical example: Clock in a new set of

frequency dividers (i.e. change the RF frequency).

Registers to be written are located in i, i+1, i+2.

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