ML7406 datasheet(64/104 Pages) ETC2

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FEDL7406-02

ML7406

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○CCA (Clear Channel Assessment) function

ML7406 supports CCA function. CCA function is to make a judment wheher the specified frequency channel is in-use or

available. Normal mode, continuous mode and IDLE detection mode are supported as following table.

[CCA mode setting]

[CCA_CTRL: B0 0x39]

Bit4 (CCA_EN)

Bit5 (CCA_CPU_EN)

Bit6 (CCA_IDLE_EN)

Normal mode

0b1

0b0

Continuous mode

0b1

0b0

IDLE detection mode

0b1

0b0

0b1

(1) Normal mode

Normal mode determines IDLE or BUSY. CCA (Normal mode) will be executed when RX_ON is issued while

CCA_EN(CCA_CTRL: B0 0x39(4)])=0b1, CCA_CPU_EN(CCA_CTRL: B0 0x39(5)])=0b0 and CCA_IDLE_EN

(CCA_CTRL: B0 0x39(6)])=0b0 are set.

Judgement of CCA is determined by average ED value and CCA threshold value defined by [CCA_LVL: B0 0x37] register.

IF average ED value in [ED_RSLT: B0 0x3A] register exceeds the CCA threshold value, it is considered as “BUSY”. And

CCA_RSLT[1:0]([CCA_CTRL: B0 0x39(1-0)]) =0b01 is set

If average ED value is smaller than CCA threshold value and maintains IDLE detection period which is defined by

IDLE_WAIT[9:0] of the [IDLE_WAIT_L: B0 0x3B], [IDLE_WAIT_H: B0 0x3C] registers. it is considered as “IDLE”.

And CCA_RSLT[1:0]([CCA_CTRL: B0 0x39(1-0)])=0b00 is set. For details operation of CCA_IDLE_WAIT[9:0], please

refer to ”IDLE detection for long time period”

If BUSY or IDLE state is detected, CCA completion interrupt (INT[18] group3) is generated, CCA_EN bit is cleared to

0b0 automatically.

Upon clearing CCA completion interrupt, CCA_RSLT[1:0]([CCA_CTRL: B0 0x39(1-0)]) are reset to 0b00. Therefore

CCA_RSLT[1:0] should be read before clearing CCA completion interrupt.

If ED value exceeds the value defined by [CCA_IGNORE_LVL: B0 0x36] register, and as long as a given ED value is

included in the averaging target of ED value calculation, IDLE judgement is not performed. In this case if average ED value

exceeds CCA threshold value, it is considered as “BUSY” and CCA is terminated.

If average ED value is smaller than CCA threshold valu, IDLE judgement is not determined. And CCA_RSLT[1:0]

([CCA_CTRL: B0 0x39(1-0)]) indicates 0b11. CCA operation continues until BUSY is determined or gievn ED value is out

of averaging target and IDLE is determined. For details operation of ED value execeeding [CCA_IGNORE_LVL: B0 0x36]

Timming from CCA command issue to CCA completion is in the formula below.

[IDLE detection]

CCA execution timing = (ED value average times + IDLE_WAIT setting) * AD conversion time

[BUSY detection]

CCA execution time = ED value average time * AD conversion time

(Note)

1. Above formula does not consider IDLE judgement exclusion based on [CCA_IGNORE_LVL: B0 0x36] register.

For details, please refer to ”IDLE detection exclusion under strong signal input”.

2. AD conversion time can be slected by ADC_CLK_SEL([ADC_CLK_SET: B1 0x08(4)]).

ADC_CLK_SEL=0b0:17.7μs , 0b1:16μs(default)

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