NXP Semiconductors DRM050 Reference Manual
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Receiver FirmwareDesigner Reference Manual DRM050 — Rev 044 Receiver Firmware MOTOROLA8.3 Remote WakeupThe JB16 receiver supports remote wakeup function that can wake upthe host computer during USB suspend.During suspend, the MCU will be periodically woken up by the IRQdriven by the external RC charging and discharging circuit. The MCUthen turns on the RF circuit (both RFW-D100 and RFW-D102) for a shortperiod of time, detect whether a valid mouse or keyboard RF packetarrived for waking up the host. During this short period, the IRQ will servefor RFW-D100 interrupt events again.If no valid packet has been detected in this period, the receiver will sleepagain. The MCU will initiate the charging and discharging cycle againbefore it enters power saving mode.The mouse or keyboard can re-transmit an RF packet again if there is noacknowledgment from the JB16 receiver. The maximum number of suchre-transmissions can be adjusted through the MAC application interfacetransmission function.For the JB16 receiver to be able to detect the incoming packet, sometiming parameters needed to be considered.The first is the small wakeup duration at each IRQ wakeup. For example,if the receiver is sleeping while a packet arrives, the transmitter will sendout a second packet because there is no acknowledge from the receiver.If the IRQ wakeup period longer than the interval between the first andnext re-transmitted packet, the re-transmitted packet can be detected bythe receiver.Another timing is the interval between two IRQ interrupts. Consider asingle key has been pressed on the keyboard. If an IRQ wakeupdetection duty in the receiver has just elapsed before the arrival of thefirst RF keyboard packet, the receiver cannot detect that packet. Thenext wakeup duty will start at the next IRQ interrupt.It can be seen that for a smaller number of re-transmission setting in thekeyboard, all re-transmission may have taken place before the nextwakeup duty start. This means the receiver will fail to detect the pressedkey and cannot wake up the host. Therefore, the interval between twoIRQ interrupts should be shorter for a relative small re-transmissionsetting in the transmitter. This time interval can be adjusted by theexternal RC values, C22, and R45.Freescale Semiconductor, IFreescale Semiconductor, Inc.For More Information On This Product,Go to: www.freescale.comnc... |
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