MRF24J40-ISLASHT datasheet(89/156 Pages) MICROCHIP

89 / 156 page

Preliminary

DS39776C-page 89

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

Bit 1

Bit 0

0x2A SOFTRST

RSTPWR

RSTBB

RSTMAC

0x36 RFCTL

WAKECNT8

WAKECNT7

RFRST

RFTXMODE

RFRXMODE

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