Application Note
MN87400/401
MN87400/401
RSSI/Carrier Sense Sequence
Semiconductor Business Division
AIS Company
Panasonic Corporation
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AP-MN87400_401-003
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Application Note
MN87400/401
CONTENTS
1
PURPOSE .......................................................................................................................... 3
2
RSSI MEASUREMENT SEQUENCE............................................................................... 3
2.1
SETTING AT STARTUP ...................................................................................................... 3
2.2
SETTING PROCEDURE FOR RSSI MEASUREMENT .......................................................... 4
2.2.1
When Diversity Is Not Used................................................................................. 4
2.2.2
When Diversity Is Used........................................................................................ 5
2.3
3
RSSI MEASUREMENT RESULT ....................................................................................... 6
CARRIER SENSE SEQUENCE........................................................................................ 8
3.1
SETTING AT STARTUP ...................................................................................................... 8
3.2
PROCEDURE FOR CARRIER SENSE .................................................................................. 9
3.2.1
When Diversity Is Not Used................................................................................. 9
3.2.2
When Diversity Is Used...................................................................................... 12
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MN87400/401
1 Purpose
This application note provides the sequence for performing RSSI measurement and
pre-transmission carrier sense by using MN87400/401.
2 RSSI Measurement Sequence
When issuing an RSSI measurement request while the chip operation mode is set to TRX
mode, the measurement result may be largely different from the actual signal level
depending on the state inside the chip. To perform RSSI measurement accurately, carry out
the measurement through the following sequence.
2.1
Setting at Startup
Set the RF_RXSTART_PARA (RF setting parameter stored at the frame memory
addresses of 3a0h or later) as follows:
Offset
Command
3a0h
0Ah
3a1h
01h 8Ah
3a3h
03h 8Ah
3a5h
43h 81h
3a7h
1Fh 85h
3a9h
61h BFh
The setting are same as application not “AP-MN87400/401-004 (basic setting example)”.
Set the PERI_CNT1 register (140h) ,antenna controlling register, to diversity OFF mode.
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MN87400/401
2.2
Setting Procedure for RSSI Measurement
Use the following sequence to measure RSSI. The sequence varies depending on
whether diversity is used or not.
The register value depending on whether the LSI version is ES or others. Refer to the
application note "AP_MN87400_004_Basic_setting_ex" for the judgment method of the LSI
version.
2.2.1
When Diversity Is Not Used
1. Set the chip operation mode to RXWAIT.
(Set bit[1] of the OPE_MODE register (000h) to 0.
Setting example: RW 000h, 0F39h)
2. Change the adjustment value of RF.
ES : (Set the RC_TRIM register (206h) to 037Fh.
Setting example: RW 206h, 037Fh)
Others : (Set the RC_TRIM register (206h) to 010Fh.
Setting example: RW 206h, 010Fh)
3. Set the RSSI measurement request.
(Set bit[3] of the RXFRMCTR register (005h) to 1.
Setting example: RW 005h, 0008h)
4. Set the chip operation mode to TRX.
(Set bit[1] of the OPE_MODE register (000h) to 1.
Setting example: RW 000h, 0F3Bh)
5. Read the RSSI values, after the measurement completion that can be known using an
RSSI complete interrupt or other interrupts.
(Read bit[15:8] of the RXFRMCTR register (005h). )
6. Reset the adjustment value of RF.
ES : (Set the RC_TRIM register (206h) to 0377h.
Setting example: RW 206h, 0377h)
Others : (Set the RC_TRIM register (206h) to 0000h.
Setting example: RW 206h, 0000h)
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Application Note
MN87400/401
2.2.2
When Diversity Is Used
Stop the diversity operation once and perform RSSI measurement using an antenna
specified with the PERI_CNT1 register. After the RSSI measurement, restart the diversity
operation.
1. Set the chip operation mode to RXWAIT.
(Set bit[1] of the OPE_MODE register (000h) to 0.
Setting example: RW 000h, 0F39h)
2. Set the diversity to OFF.
(Set bit[15] of the DIVER register (126h) to 0.
Setting example: RW 126h, 005Fh)
3. Change the adjustment value of RF.
ES : (Set the RC_TRIM register (206h) to 037Fh.
Setting example: RW 206h, 037Fh)
Others : (Set the RC_TRIM register (206h) to 010Fh.
Setting example: RW 206h, 010Fh)
4. Set the RSSI measurement request.
(Set bit[3] of the RXFRMCTR register (005h) to 1.
Setting example: RW 005h, 0008h)
5. Set the chip operation mode to TRX.
(Set bit[1] of the OPE_MODE register (000h) to 1.
Setting example: RW 000h, 0F3Bh)
6. Read the RSSI values, after the measurement completion that can be known using an
RSSI complete interrupt or other interrupts.
(Read bit[15:8] of the RXFRMCTR register (005h). )
7. Set the chip operation mode to RXWAIT.
(Set bit[1] of the OPE_MODE register (000h) to 0.
Setting example: RW 000h, 0F39h)
8. Reset the adjustment value of RF.
ES : (Set the RC_TRIM register (206h) to 0377h.
Setting example: RW 206h, 0377h)
Others : (Set the RC_TRIM register (206h) to 0000h.
Setting example: RW 206h, 0000h)
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MN87400/401
9. Set the diversity to ON.
(Set bit[15] of the DIVER register (126h) to 1.
Setting example: RW 126h, 805Fh)
10. Set the chip operation mode to TRX.
(Set bit[1] of the OPE_MODE register (000h) to 1.
Setting example: RW 000h, 0F3Bh)
2.3
RSSI Measurement Result
The measurement conditions are as follows:
Center frequency: 920 MHz / 2440 MHz
Bit rate：100 Kbps
Measurement temperature: 25°C
The RSSI measurement result for MN87400 at the center frequency of 920 MHz is as
follows:
Input wave is a non-modulated signal with the center frequency (Fc) of 920 MHz.
The guaranteed operation range is between -95 dBm and -10 dBm.
RSSI measurement result
Center freq=920MHz
140
-95dBm
-10dBm
120
Register (DEC)
100
80
60
40
20
Guaranteed operation range
0
-120
-100
-80
-60
-40
-20
0
Input Level [dBm]
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Application Note
MN87400/401
The RSSI measurement result for MN87400 at the center frequency of 2440 MHz is as
follows:
Input wave is a non-modulated signal with the center frequency (Fc) of 2440 MHz.
The guaranteed operation range is between -95 dBm and -30 dBm.
RSSI measurement result
Center freq=2440MHz
120
-95dBm
-30dBm
100
Register (DEC)
80
60
40
20
Guaranteed operation range
0
-120
-100
-80
-60
-40
Input Level [dBm]
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Application Note
MN87400/401
3 Carrier Sense Sequence
When performing carrier sense before transmission, the state of the carrier may be false
detected due to RSSI measurement error. To reduce the probability of false detection, use
the following sequence. In addition, automatic back-off function before frame transmission
cannot be used.
3.1
Setting at Startup
Make the settings same as the RSSI measurement.
To stop the automatic back-off before frame transmission, set bit[11] of the OPE_MODE
register (000h) to 1.
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MN87400/401
3.2
Procedure for Carrier Sense
Use the following sequence to execute carrier sense. The sequence varies depending on
whether diversity is used or not.
3.2.1
When Diversity Is Not Used
1. Set the chip operation mode to RXWAIT.
(Set bit[1] of the OPE_MODE register (000h) to 0.
Setting example: RW 000h, 0F39h)
2. Change the adjustment value of RF.
ES : (Set the RC_TRIM register (206h) to 037Fh.
Setting example: RW 206h, 037Fh)
Others : (Set the RC_TRIM register (206h) to 010Fh.
Setting example: RW 206h, 010Fh)
3. Set AGC to the maximum gain fixed mode.
(Set bit[7] of the AGC_CTR register (10bh) to 1.
Setting example: RW 10bh, 0D8Fh)
4. Set the value of SYNC_DELAY to 0.
(Set bit[15:8] of the SFDTIMEOUT register (108h) to 00h.
Setting example: RW 108h, 000Ah)
5. Set the back-off request.
(Set bit[6] of the TXFRMCTR register (004h) to 1.
Setting example: RW 004h, 0040h)
6. Set the chip operation mode to TRX.
(Set bit[1] of the OPE_MODE register (000h) to 1.
Setting example: RW 000h, 0F3Bh)
7. Read the back-off result, after the measurement completion that can be known
using a back-off complete interrupt or other interrupts.
(Read bit[7] of the TXFRMCTR register (004h). )
When bit[7]=1 , The channel is IDLE. When bit[7]=0 , The channel is BUSY.)
8. Reset the adjustment value of RF.
ES : (Set the RC_TRIM register (206h) to 0377h.
Setting example: RW 206h, 0377h)
Others : (Set the RC_TRIM register (206h) to 0000h.
Setting example: RW 206h, 0000h)
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MN87400/401
9. Cancel the gain fixed mode of AGC.
(Set bit[7] of the AGC_CTR register (10bh) to 0.
Setting example: RW 10bh, 0D7Fh)
10. Set the value of SYNC_DELAY to 25h.
(Set bit[15:8] of the SFDTIMEOUT register (108h) to 25h.
Setting example: RW 108h, 250Ah)
After the back-off is done in step 7, if not busy, start a frame transmission (with no
automatic back-off). Refer to the application note "AP_MN87400_002_FrameTXRX" for the
frame transmission method.
When performing a carrier sense before transmission while widening the channel width,
insert the channel filter setting before step 3. To ensure the reception performance, re-set
the channel filter according to the reception signal band, after executing carrier sense.
When not performing ACK frame reception, it is no problem to make the re-setting of
channel filter and the settings in steps 8, 9 and 10 after transmission is completed.
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Application Note
MN87400/401
The following is a result of executing a carrier sense after setting the system so that the
carrier is detected as "busy" at an input level of -90 dBm. The error of RSSI detection is
around 1 dB, thereby producing a difference of 1 dB in the detection result, however
operation is stable.
Measurement Conditions:
Center frequency = 920 MHz GFSK 100 Kbps (M = 1.0)
Number of executions = 300 times for each input level
Setting of detection value =1Dh (RW 10c 1d 15)
Carrier detection = Repeating 3 times (RW 013 01 02)
Carrier Sense Detection Result(Detect Threshold=-90dBm)
120.0%
THRESHOLD
IDLE Detection Probability
100.0%
80.0%
Board A
Board B
Board C
60.0%
40.0%
20.0%
0.0%
-92
-91
-90
-89
Input Signal Strength (dBm)
11
-88
AP-MN87400_401-003
REV1.0
Application Note
MN87400/401
3.2.2
When Diversity Is Used
Stop the diversity operation once and perform a carrier sense and transmission using an
antenna specified with the PERI_CNT1 register. After the transmission, restore the diversity
operation.
1. Set the chip operation mode to RXWAIT.
(Set bit[1] of the OPE_MODE register (000h) to 0.
Setting example: RW 000h, 0F39h)
2. Set the diversity to OFF.
(Set bit[15] of the DIVER register (126h) to 0.
Setting example: RW 126h, 005Fh)
3. Change the adjustment value of RF.
ES : (Set the RC_TRIM register (206h) to 037Fh.
Setting example: RW 206h, 037Fh)
Others : (Set the RC_TRIM register (206h) to 010Fh.
Setting example: RW 206h, 010Fh)
4. Set AGC to the maximum gain fixed mode.
(Set bit[7] of the AGC_CTR register (10bh) to 1.
Setting example: RW 10bh, 0D8Fh)
5. Set the value of SYNC_DELAY to 0.
(Set bit[15:8] of the SFDTIMEOUT register (108h) to 00h.
Setting example: RW 108h, 000Ah)
6. Set the back-off request.
(Set bit[6] of the TXFRMCTR register (004h) to 1.
Setting example: RW 004h, 0040h)
7. Set the chip operation mode to TRX.
(Set bit[1] of the OPE_MODE register (000h) to 1.
Setting example: RW 000h, 0F3Bh)
8. Read the back-off result, after the measurement completion that can be known
using a back-off complete interrupt or other interrupts.
(Read bit[7] of the TXFRMCTR register (004h). )
When bit[7]=1 , The channel is IDLE. When bit[7]=0 , The channel is BUSY.)
9. Reset the adjustment value of RF.
ES : (Set the RC_TRIM register (206h) to 0377h.
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MN87400/401
Setting example: RW 206h, 0377h)
Others : (Set the RC_TRIM register (206h) to 0000h.
Setting example: RW 206h, 0000h)
10. Cancel the gain fixed mode of AGC.
(Set bit[7] of the AGC_CTR register (10bh) to 0.
Setting example: RW 10bh, 0D7Fh)
11. Set the value of SYNC_DELAY to 25h.
(Set bit[15:8] of the SFDTIMEOUT register (108h) to 25h.
Setting example: RW 108h, 250Ah)
12. Set the chip operation mode to RXWAIT.
(Set bit[1] of the OPE_MODE register (000h) to 0.
Setting example: RW 000h, 0F39h)
13. Set the diversity to ON.
(Set bit[15] of the DIVER register (126h) to 1.
Setting example: RW 126h, 805Fh)
14. Set the chip operation mode to TRX.
(Set bit[1] of the OPE_MODE register (000h) to 1.
Setting example: RW 000h, 0F3Bh)
After the back-off is done in step 8, if not busy, start a frame transmission (with no
automatic back-off). Refer to the application note "AP_MN87400_002_FrameTXRX" for the
frame transmission method.
When performing a carrier sense before transmission while widening the channel width,
insert the channel filter setting before step 4. To ensure the reception performance, re-set
the channel filter according to the reception signal band, after executing carrier sense.
When not performing ACK frame reception, it is no problem to make the re-setting of
channel filter and the settings in steps from 9. to 14.after transmission is completed.
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