MRF24XA_15 Datasheet, PDF (53/258 Pages) Microchip Technology – Low-Power, 2.4 GHz ISM-Band IEEE 802.15.4™ RF

MRF24XA
REGISTER 2-36: CCACON1 (CCA CONTROL 1 REGISTER)
R/HS/HC-0 R/W/HC-0
R/W-001100
CCABUSY CCAST
RSSITHR<5:0>
bit 7
ADDRESS: 0x2F
bit 0
Legend: R = Readable bit W = Writable bit
-n = Value at POR
‘1’ = Bit is set
r = Reserved
HC = Hardware Clear
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
HS = Hardware Set
bit 7
bit 6
bit 5-0
Note 1:
2:
CCABUSY: Clear Channel Assessment Busy Flag bit
This bit represents the result of the latest CCA measurement.
1 = Medium is busy
0 = Medium is silent
CCAST: Clear Channel Assessment Start bit⁽¹⁾
Setting this register bit triggers MCU to start a new CCA measurement. The hardware clears this bit
when the CCA measurement is done (EDCCAIF is set) and CCABUSY is valid.
RSSITHR<5:0>: RSSI Threshold bits⁽²⁾
This threshold is used in CCA operation when Energy detect or Energy and Carrier Sense mode is
selected.
Representation: resolution of 2 dB/LSB, RSSITHR = 0x10 represents ca. -75 dBm noise level. Note that
this threshold may be different with other matching network or antenna.
RX chain must be turned on (RXEN = 1) to perform this measurement. Packet reception is not disabled
during the measurement, main purpose is testing.
In the corresponding CCA modes the radio measures EDMEAN<7:0>. If EDMEAN<7:2> is greater than
RSSITHR<5:0>, CCABUSY is set. Example: To set the RSSI threshold where the chip measures 0x30
EDMEAN, RSSITHR<5:0> must be 0x0C.
REGISTER 2-37:
bit 7
CCACON2 (CCA CONTROL 2 REGISTER)
R-0
R/W-01
CSTHR<3:0>
CCALEN<1:0>
ADDRESS: 0x30
R/W-01
CCAMODE<1:0>
bit 0
Legend: R = Readable bit W = Writable bit
-n = Value at POR
‘1’ = Bit is set
r = Reserved
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 7-4
bit 3-2
bit 1-0
Note 1:
2:
CSTHR<3:0>: Carrier Sense Threshold Field bits. This threshold is used in CCA operation when
Carrier Sense mode is selected.
CCALEN<1:0>: Clear Channel Assessment Length bits⁽¹⁾
Value N indicates duration of 2^N * 32 µs.
CCAMODE<1:0>: Clear Channel Assessment Mode Field bits⁽²⁾
11 = CCA Mode 3/a in the IEEE 802.15.4 standard: Energy AND Carrier Sense Threshold
10 = CCA Mode 2 in the IEEE 802.15.4 standard: Carrier Sense Threshold
01 = CCA Mode 1 in the IEEE 802.15.4 standard: Energy Detect Threshold (default)
00 = CCA Mode 3/b in the IEEE 802.15.4 standard: Energy OR Carrier Sense Threshold
The IEEE 802.15.4 standard requires 128 µs, but shorter length is recommended when using higher rates
with optimized Preamble mode (RATECON.OPTIMAL = 1).
The measured RSSI result is stored in EDMEAN<7:0> register in all modes except Mode 2.
 2015 Microchip Technology Inc.
Preliminary
DS70005023C-page 53