Receiver Configuration
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SPRUI07–March 2020
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Multichannel Buffered Serial Port (McBSP)
12.8.13 Receive Sign-Extension and Justification Mode
The RJUST bits (see Table 12-32) determine whether data received by the McBSP is sign-extended and
how it is justified.
Table 12-32. Register Bits Used to Set the Receive Sign-Extension and Justification Mode
Register Bit Name Function Type
Reset
Value
SPCR1 14-13 RJUST Receive sign-extension and justification mode R/W 00
RJUST = 00 Right justify data and zero fill MSBs in DRR[1,2]
RJUST = 01 Right justify data and sign extend it into the MSBs in
DRR[1,2]
RJUST = 10 Left justify data and zero fill LSBs in DRR[1,2]
RJUST = 11 Reserved
12.8.13.1 Sign-Extension and the Justification
RJUST in SPCR1 selects whether data in RBR[1,2] is right- or left-justified (with respect to the MSB) in
DRR[1,2] and whether unused bits in DRR[1,2] are filled with zeros or with sign bits.
Table 12-33 and Table 12-34 show the effects of various RJUST values. The first table shows the effect
on an example 12-bit receive-data value ABCh. The second table shows the effect on an example 20-bit
receive-data value ABCDEh.
Table 12-33. Example: Use of RJUST Field With 12-Bit Data Value ABCh
RJUST Justification Extension
Value in
DRR2
Value in
DRR1
00b Right Zero fill MSBs 0000h 0ABCh
01b Right Sign extend data into MSBs FFFFh FABCh
10b Left Zero fill LSBs 0000h ABC0h
11b Reserved Reserved Reserved Reserved
Table 12-34. Example: Use of RJUST Field With 20-Bit Data Value ABCDEh
RJUST Justification Extension
Value in
DRR2
Value in
DRR1
00b Right Zero fill MSBs 000Ah BCDEh
01b Right Sign extend data into MSBs FFFAh BCDEh
10b Left Zero fill LSBs ABCDh E000h
11b Reserved Reserved Reserved Reserved
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