DR
Framing bit
B5
B6
B7
FSR
CLKR
ÁÁ
ÁÁ
ÁÁ
ÁÁ
2-bit delay
Receiver Configuration
1087
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Multichannel Buffered Serial Port (McBSP)
Figure 15-47. 2-Bit Data Delay Used to Skip a Framing Bit
15.8.13 Set the Receive Sign-Extension and Justification Mode
The RJUST bits (see
) determine whether data received by the McBSP is sign-extended and
how it is justified.
Table 15-32. 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
15.8.13.1 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.
and
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 15-33. 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 15-34. 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