Using the Driver
9.5
Buffer Formats
<-------
8 bits
------->
Preamble/ID repeats
Spacing (in bit times)
<-------
8 bits
------->
Chec
Bank
flag
RSSI
flag
ID
RSSI (5 bits)
ksum
Full
Full
flag
Length (7 bits)
Length (7 bits)
flag
Data 0
Data 0
.
.
.
.
.
.
.
.
Data N (max. 127)
Data N (max. 127)
Tx Buffer
Rx Buffer
Figure 11. Buffer Formats
9.5.1
Preamble/ID Repeats
When using the Echo_SendMessageservice, this byte defines the number of times to repeat the preamble/ID
sequence before sending the data.
9.5.2
Spacing
When using the Echo_SendMessageservice, this byte defines the number of bit-times to leave between
repetitions of the preamble/ID sequence.
9.5.3
ID
The message ID. The actual number of bits sent for the ID depends on the configuration option
ECHO_ID_LENGTHin the driver header file. If the length is less than eight, the bits used correspond to the least
significant bits in this byte.
9.5.4
Full Flag
The full flag indicates when the buffer is in use, either by the driver (for the Tx buffer) or by the application
(for the Rx buffer). Using this bit limits the maximum data length to 127 bytes.
When any of the message sending services are called, the buffer is marked full for the duration of its use
by the driver. Only when the driver clears the full flag can the transmit buffer be modified again. Modifying
it while this bit is set can lead to corruption of the messages sent or other undesirable and unpredictable
effects.
Software Drivers for MC33696, Rev. 1
Freescale Semiconductor
17
FREESCALE [ Freescale ]
