Table of Contents
Advertisement
MPC850(A) and MPC850(B) exchange transparent frames and synchronize each other
using RTS and CD. However, CTS is not required because transmission begins at any time.
Thus, RTS is connected directly to the other MPC850 CD pin. GSMR_H[RSYN] is not
used and transmission and reception from each MPC850 are independent.
28.4.1.3 Transparent Mode without Explicit Synchronization
If there is no need to synchronize the transparent controller at a specific point, the user can
'fake' synchronization in one of the following ways:
• Tie a parallel I/O pin to the CTS and CD lines. Then, after enabling the receiver and
transmitter, provide a falling edge by manipulating the I/O pin in software.
• Enable the receiver and transmitter for the SCC in loopback mode and then change
GSMR_L[DIAG] to 0b00 while the transmitter and receiver and enabled.
28.4.1.4 End of Frame Detection
An end of frame cannot be detected in the transparent data stream since there is no defined
closing flag in transparent mode. Therefore, if framing is needed, the user must use the CD
line to alert the transparent controller of an end of frame.
28.4.2 Synchronization and the TSA
A transparent-mode SCC using the time-slot assigner can synchronize either on a
user-defined in-line pattern or by inherent synchronization.
Note that when using the TSA, a newly-enabled transmitter sends from 10 to 15 frames of
idles before sending the actual transparent data due to start-up requirements of the TDM.
Therefore, when loopback testing through the TDM, expect to receive several bytes of 0xFF
before the actual data.
28.4.2.1 In-line Synchronization Pattern
The receiver can be programmed to begin receiving data into the receive buffers only after
a specified data pattern arrives. To synchronize on an in-line pattern:
• Set GSMR_H[SYNL].
• Program the DSR with the desired pattern.
• Clear GSMR_H[CDP].
• Set GSMR_H[CTSP, CTSS, CDS].
If GSMR_H[TXSY] is also used, the transmitter begins transmission eight clocks after the
receiver achieves synchronization.
Achieving Synchronization in Transparent Mode
Chapter 28. SCC Transparent Mode
Advertisement
Chapters
Table of Contents
