RSSI/Carrier Sense Sequence Semiconductor Business Division AIS Company Panasonic Corporation 1 AP-MN87400_401-003
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 RSSI MEASUREMENT RESULT... 6 3 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 2 AP-MN87400_401-003
1 Purpose This application note provides the sequence for performing RSSI measurement and pre-transmission carrier sense by using. 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--004 (basic setting example). Set the PERI_CNT1 register (140h),antenna controlling register, to diversity OFF mode. 3 AP-MN87400_401-003
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) 4 AP-MN87400_401-003
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) 5 AP-MN87400_401-003
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. -95dBm RSSI measurement result Center freq=920mhz -10dBm 140 120 Register (DEC) 100 80 60 40 Guaranteed operation range -120-100 -80-60 -40-20 0 Input Level [dbm] 20 0 6 AP-MN87400_401-003
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. -95dBm RSSI measurement result Center freq=2440mhz -30dBm 120 100 Register (DEC) 80 60 40 Guaranteed operation range -120-100 -80-60 -40 Input Level [dbm] 20 0 7 AP-MN87400_401-003
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. 8 AP-MN87400_401-003
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) 9 AP-MN87400_401-003
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. 10 AP-MN87400_401-003
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 100.0% IDLE Detection Probability 80.0% 60.0% 40.0% Board A Board B Board C 20.0% 0.0% -92-91 -90-89 -88 Input Signal Strength (dbm) 11 AP-MN87400_401-003
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. 12 AP-MN87400_401-003
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. 13 AP-MN87400_401-003
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