Micrel

MICRF405

April 2006

9

M9999-041906

(408) 955-1690

Writing to the Control Registers in MICRF405

Writing: A number of octets are entered into

MICRF405 followed by a load-signal to activate the

new setting. Making these events is referred to as a

“write sequence.” It is possible to update all, 1, or n

control registers in a write sequence. The address to

write to (or the first address to write to) can be any

valid address (0-29). The SIO line is always an input

to the MICRF405 (output from user) when writing.

What to write:

• The address of the control register to write to (or

if more than 1 control register should be written

to, the address of the 1st control register to write

to).

• A bit to enable reading or writing of the control

registers. This bit is called the R/W bit.

• The values to write into the control register(s).

Field

Comments

Address:

A 7-bit field, ranging from 0 to 29. MSB is written first.

R/W bit:

A 1-bit field, = “0” for writing

Values:

A number of octets (1-30 octets). MSB in every octet is written first. The first octet is written to the control

register with the specified address (=”Address”). The next octet (if there is one) is written to the control

register with address = “Address + 1” and so on.

Table 3. Writing to the Control Registers.

How to write:

Bring SEN low to start a write sequence. The active

state of the SEN line is “low”. Use the SCK/SIO

serial interface to clock in “Address” and “R/W” bit

and “Values” into the MICRF405. MICRF405 will

sample the SIO line at negative edges of SCK. Make

sure to change the state of the SIO line before the

negative edge, for instance on positive edge. Refer

to Figure 2.

Bring SEN inactive to make an internal load-signal

and complete the write-sequence. Note: there is an

exception to this point. If the programming bit called

“load_en” (D0 in ControlRegister0) is “0”, then no

load pulse is generated.

The two different ways to “program the chip”

are:

• Write to a number of control registers (0-29)

when the registers have incremental addresses

(write to 1, all or n registers)

• Write to a number of control registers when the

registers have non-incremental addresses.

Writing to a Single Register

Writing to a control register with address “A6, A5,

…A0” is described here. During operation, writing to

1 register is sufficient to change the way the

transmitter works. Typical example: Change from

transmit mode to power-down.

Field

Comments

Address:

7 bit = A6, A5, …A0 (A6 = MSB. A0 = LSB)

R/W bit:

“0” for writing

Values:

8 bits = D7, D6, …D0 (D7 = MSB, D0 = LSB)

Table 4. When writing to a Single Register, totally 2 octets are clocked into the MICRF405.

How to write:

• Bring SEN low

• Use SCK and SIO to clock in the 2 octets

• Bring SEN high