ML7344J datasheet(71/151 Pages) ETC2

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FEDL7344C/E/J-04

ML7344C/E/J

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●CCA (Clear Channel Assessment) function

ML7344 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

whille 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.

CCA judgement is determined by average ED value in [ED_RSLT: B0 0x3A] register and CCA threshold

value defined by [CCA_LVL: B0 0x37] register. IF average ED value 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] =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] are reset to 0b00. Therefore CCA_RSLT[1:0]

should be read before clearing CCA completion interrupt.

If an ED value exceeds the value defined by [CCA_IGNORE_LVL: B0 0x36] register, and 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 exceed CCA threshold value, it is considered as “BUSY” and CCA operation is terminated.

If average ED value is smaller than CCA threshold value, IDLE judgement is not determined. And

CCA_RSLT[1:0] indicates 0b11. CCA operation continues until “BUSY” is determined or the gievn ED value

is out of averaging target and “IDLE” is determined. For details operation of ED value execeeding

[CCA_IGNORE_LVL: B0 0x36] register, please refer to ”IDLE determination exclusion under strong signal

input”.

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

[IDLE detection]

CCA execution time = (ED value average times + Dgital filter delay + IDLE_WAIT setting) *

AD conversion time

[BUSY detection]

CCA execution time = (ED value average times + Digtal filter delay)* AD conversion time

NOTE:

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

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

ADC_CLK_SEL=0b0:14.7μs , 0b1:18.5μs (default)

3. Digital filter delay is “AD conversion time * 8”.

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