Freescale Semiconductor MSC8156 Evaluation Module MSC8156EVM MSC8156EVM Benutzerhandbuch

Freescale Semiconductor

 

19-27

the status bit. When the interrupt is asserted in the EPIC, then the SC3850 core can fill all the 
transmit buffers from their beginnings to the byte to which the second threshold (TDBST) points. 
Meanwhile, the TDM keeps reading new data from the buffer. 

Figure 19-26 shows the threshold pointers for transparent and A/

μ law channels. 

The TDMxRDBFT[RDBFT], TDMxRDBST[RDBST], TDMxTDBFT[TDBFT], and 
TDMxTDBST[TDBST] fields are control fields and can therefore be updated while the TDM is 
active. For example, to invoke an interrupt for each 64 bits written to the system I/F memory, the 
interrupt routine that handles the receive first threshold interrupt should include:

If (TDMxRDBFT[RDBFT] == (TDMxRDBS[RDBS] - 0xF))

then TDMxRDBFT[RDBFT] = 0x0

else if (TDMxRDBFT[RDBFT] == (TDMxRDBS[RDBS] - 0x7))

then TDMxRDBFT[RDBFT] = 0x8

else TDMxRDBFT[RDBFT] = TDMxRDBFT[RDBFT] + 0x10

The interrupt routine that handles the receive second threshold interrupt should include:

If (TDMxRDBST[RDBST] == (TDMxRDBS[RDBS] - 0xF))

then TDMxRDBST[RDBST] = 0x0

else if (TDMxRDBST[RDBST] == (TDMxRDBS[RDBS] - 0x7))

then TDMxRDBST[RDBST] = 0x8

else TDMxRDBST[RDBST] = TDMxRDBST[RDBST] + 0x10

Figure 19-26.  Main Memory Buffers Threshold Pointers

Transparent Channel

A/

μ

 Law Channel

Buf

fer Siz

e

RDBS/TDBS

First Threshold

Second Threshold

First Threshold

(RDBFT/TDBFT) 

×

 2

Second Threshold

(RDBST/TDBST) 

×

 2

Bu

ff

e

r Siz

e

2

 ×

 RDBS / 2

 

×

 TDBS

Displacement

RDBFT/TDBFT

RDBST/TDBST

TDBDR/RDBDR

Displacement

(TDBDR/RDBDR) 

×

 2

Data Buffer of

Data Buffer of