MC33596_10 Datasheet, PDF (17/70 Pages) Freescale Semiconductor, Inc – PLL Tuned UHF Receiver for Data Transfer Applications

Receive Mode
11.2.3.3 HEADER
The HEADER defines the beginning of the message, as it is compared with the HEADER register. Its
length is variable, defined by the HDL[1:0] bits. The complement of the header is also recognized as the
header—in this case, output data is complemented. The header and its complement should not be part of
the ID.
The ID and the header are sent at the same data rate as data.
11.2.3.4 Data and EOM
The data must follow the header, with no delay.
The message is completed with an end-of-message (EOM), consisting of two consecutive NRZ ones or
zeroes (i.e., a Manchester code violation). Even in the case of FSK modulation, data must conclude with
an EOM, and not simply by stopping the RF transmission.
11.2.4 State Machine in Receive Mode When DME=1
When the strobe oscillator is enabled (SOE = 1), the receiver is continuously cycling on/off. The ID must
be recognized for the receiver to stay on. Consequently, the transmitted ID burst must be long enough to
include two consecutive receiver-on cycles.
When the strobe oscillator is not enabled (SOE = 0), these timing constraints must be respected by the
external control applied to pin STROBE.
Figure 11 shows the correct detection of an ID when STROBE is controled internally using the strobe
oscillator (SOE=1) or externally by the MCU (SOE=0).
RF
Signal
Preamble ID
ID ID
ID
ID ID
ID
ID Field
Header
Data EOM
Receiver
Status
On
Off
On
Off
SPI
Output
On Time
Off Time
ID
Detected
Data
Figure 10. Complete Transmission with ID Detection
Two different processes are possible, as determined by the values of the SOE bit.
11.2.4.1 Data Manager Enabled and Strobe Oscillator Enabled
Figure 11 shows the state diagram when the data manager and the strobe oscillator are enabled. In this
configuration, the receiver is controlled internally by the strobe oscillator. However, external control via
the STROBE pin is still possible, and overrides the strobe oscillator command.
MC33596 Data Sheet, Rev. 4
Freescale Semiconductor
17