GT-96100A Advanced Communication Controller
Revision 1.0
383
NOTES:When the FlexTDM is disabled, the CPU accesses the DPRAM for both reads and writes. When the
FlexTDM is enabled, the FlexTDM DPRAM is write only.
After reset the dual port RAM entries are undefined. Users must explicitly program the required entries
in order to ensure correct and consistent system operation.
15.3
FlexTDM Programing Modes
After enabling the FlexTDM, there are two ways the user can dynamically program the DPRAM: Single Array
Mode and Split Array Mode.
In Single Array Mode, the FlexTDM read pointer ALWAYS returns to entry 0 after receiving a SYNC or reading
the last entry (entry with L bit set). The entire range of 256 entries is available for programing a TDM frame. The
user can dynamically make changes in the DPRAM but precautions must be made not to write to the same
address from which the FlexTDM is reading. This can be done by checking the read pointer before accessing the
DPRAM array.
In Split Array mode, the TDM frame is limited to 128 DPRAM entries. The user programs the FlexTDM frame
in entries 0-127 and enables the FlexTDM. When a change in programming is needed, the user first programs the
new frame in entries 128-255 and than sets the R2HALF (read as “Return To Half”) bit in the TCR. When the
next SYNC or last entry occurs, the FlexTDM starts processing the frame as programmed in entries 128-255.
The user can then re-program entries 0-127. This process of switching between one half of the DPRAM and the
other half simplifies on-the-fly DPRAM changes.
NOTE: If a frame structure is changed (e.g. a change in frame length) while the FlexTDM is enabled, the
FlexTDM can lose synchronization. This can lead to a CD lost error and a CTS lost error for all chan-
nels that are connected to the FlexTDM.
1. The total number of times that a DPRAM entry is actually repeated is set by both the RPT (bits 24:23) and B (bit 18) fields. The range is 1 (B=0,
RPT=00) to 32 (B=1, RPT=11).