AN2262 Motorola / Freescale Semiconductor, AN2262 Datasheet - Page 29

• Manufacturer Part Number: AN2262
• Description: Wireless HC08 Modem
• Manufacturer: Motorola / Freescale Semiconductor

MOTOROLA
timeout no other byte is received, the timeout interrupt is activated indicating
the end of the frame. This is also shown in
The timeout length is selected at twice the length of one byte. It may
theoretically happen that one SPI read (and timeout reset) will occur
immediately after data is received, the following SPI read could be delayed due
to the other tasks. The maximum delay must be less than one byte in duration
(otherwise actual unread byte is rewritten and lost by overrun). The maximum
period between two such reads is less than two bytes (16 bits) length. The
constant is again calculated at compile time in
When the end of frame is detected, the following conditions must be met in
order to declare that the received frame is correct:
If all conditions pass, this condition is indicated to the main loop as well as when
the check conditions fail.
ACTUAL RF TRANSMISSION
SPI ACTIVITY
•
•
•
SETTLING
The received data is 4 bytes long or longer (the shortest frame consists
of 1 byte length, 1 byte data, and 2 bytes CRC) — see
The data length information (first position) must be 4 bytes or longer but
not longer than the RFRXBUFFSIZE constant. A shorter value is
meaningless, while a longer value means that such a frame can’t fit the
recipient’s receive buffer.
The CRC calculated over the complete buffer is 0.
AGC
#define RF_RXTIMEOUT 16L*RF_FULLBIT
Wireless HC08 Modem
HEADER
Figure 19. Detecting the End of the Frame
DATA #0 DATA #1 DATA #2 DATA #3
DATA #0 DATA #1 DATA #2 DATA #3
RESET
TIMER
RESET
TIMER
RESET
TIMER
Figure
rf2.h
RESET
TIMER
19.
DATA #N EOM
DATA #N EOM
RESET
TIMER
RF-08
RF_RXTIMEOUT
THRESHOLD
REACHED
TIMER
Protocol.
AN2262/D
Software
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