MRF24J40_08 Datasheet, PDF (87/152 Pages) Microchip Technology – IEEE 802.15.4™ 2.4 GHz RF Transceiver

MRF24J40
3.0 FUNCTIONAL DESCRIPTION
3.1 Reset
The MRF24J40 has four Reset types:
• Power-on Reset – The MRF24J40 has built-in
Power-on Reset circuitry that will automatically
reset all control registers when power is applied. It
is recommended to delay 2 ms after a Reset
before accessing the MRF24J40 to allow the RF
circuitry to start up and stabilize.
• RESET Pin – The MRF24J40 can be reset by the
host microcontroller by asserting the RESET pin
13 low. All control registers will be reset. The
MRF24J40 will be released from Reset approxi-
mately 250 μs after RESET is released. The
RESET pin has an internal weak pull-up resistor.
It is recommended to delay 2 ms after a Reset
before accessing the MRF24J40 to allow the RF
circuitry to start up and stabilize.
• Software Reset – A Software Reset can be
performed by the host microcontroller. The power
management circuitry is reset by setting the
RSTPWR (0x2A<2>) bit to ‘1’. The control
registers retain their values. The baseband
circuitry is reset by setting the RSTBB (0x2A<1>)
bit to ‘1’. The control registers retain their values.
The MAC circuitry is reset by setting the RSTMAC
(0x2A<0>) bit to ‘1’. All control registers will be
reset. The Resets can be performed individually
or together. The bit(s) will be automatically
cleared to ‘0’ by hardware. No delay is necessary
after a Software Reset.
• RF State Machine Reset – Perform an RF State
Machine Reset by setting to ‘1’ the RFRST
(RFCTL 0x36<2>) bit and then clearing to ‘0’.
Delay at least 192 μs after performing to allow the
RF circuitry to calibrate. The control registers
retain their values.
Note:
The RF state machine should be Reset
after the frequency channel has been
changed (RFCON0 0x200).
TABLE 3-1: REGISTERS ASSOCIATED WITH RESET
Addr. Name
Bit 7 Bit 6 Bit 5
Bit 4
Bit 3
Bit 2
0x2A SOFTRST
r
r
r
r
r
RSTPWR
0x36 RFCTL
r
r
r WAKECNT8 WAKECNT7 RFRST
Bit 1
RSTBB
r
Bit 0
RSTMAC
r
© 2008 Microchip Technology Inc.
Preliminary
DS39776B-page 85