m-LAW/A-LAW Companding Hardware Operation
11-51
Multichannel Buffered Serial Ports
Figure 11–34.
Companding Data Formats
LAW16
15 2
1
0
µ
-Law
Value
0
LAW16
15
3
2
0
A-law
Value
0
Figure 11–35.
Transmit Data Companding Format in DXR
DXR bits
31
16
15
0
Don’t care
LAW16
For reception, the 8-bit compressed data in RBR is expanded to a left-justified
16-bit data, LAW16. This can be further justified to a 32-bit data by programming
the RJUST field in the SPCR as shown in Table 11–13.
Table 11–13. Justification of Expanded Data in DRR
DRR Bits
RJUST
31 16
15 0
00
0
LAW16
01
sign
LAW16
10
LAW16
0
11
Reserved
11.4.1 Companding Internal Data
If the McBSP is otherwise unused, the companding hardware can compand
internal data. This hardware can be used to:
-
Convert linear data to the appropriate
µ
-law or A-law format
-
Convert
µ
-law or A-law data to the linear format
-
Observe the quantization effects in companding by transmitting linear
data and compressing and re-expanding this data. This is useful only if
both XCOMPAND and RCOMPAND enable the same companding format.
µ
-LAW/A-LAW Companding Hardware Operation