DRR
Receive Shift
Register
(RSR)
Receive Buffer
(RB)
DR
To CPU/DMA
Justify
and bit fill
CLKR
DR
FSR
A1
B7
B6
B5
B4
B3
B2
B1
B0
A0
C7
C6
C5
RRDY
RB to DRR copy (A)
Read from DRR (A)
RB to DRR copy (B)
Read from DRR (B)
RRDY: Status of receiver ready bit (high is 1)
Preliminary
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Architecture
11.2.1.5 McBSP Reception
This section explains the fundamental process of reception in the McBSP.
and
show how reception occurs in the McBSP.
shows the physical
path for the data.
is a timing diagram showing signal activity for one possible reception
scenario. A description of the process follows the figures.
Figure 11-7. McBSP Reception Physical Data Path
Figure 11-8. McBSP Reception Signal Activity
The following process describes how data travels from the McBSP.DR pin to the CPU or to the DMA
controller:
1. The McBSP waits for a receive frame-synchronization pulse on internal FSR.
2. When the pulse arrives, the McBSP inserts the appropriate data delay that is selected with the
RDATDLY bits of RCR2_REG[1:0] register. In the preceding timing diagram a 1-bit data delay is
selected.
3. The McBSP accepts data bits on the McBSP.DR pin and shifts them into the receive shift register.
4. When a full word is received, the McBSP copies the contents of the receive shift register to the
receive buffer, provided that RB is not full.
5. When the programmed receive threshold is reached the McBSP asserts the receiver ready bit
(RRDY) in SPCR1_REG. This indicates that receive data is ready to be read by the CPU or the
DMA controller by accessing DRR_REG register. The data copied from RB to DRR_REG is justified
and bit filled according to the RJUST bits.
6. 6. The CPU or the DMA controller reads the data from the data receive register. When the receive
buffer is empty, RRDY bit is cleared.
When activity is not properly timed, errors can occur. See the following topics for more details:
•
Overrun in the Receiver
•
Underflow in the receiver
•
Unexpected Receive Frame–Synchronization Pulse
1131
SPRUGX9 – 15 April 2011
Multichannel Buffered Serial Port (McBSP)
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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