RRDY
DR
FSR
CLKR
Read from DRR1(b)
RBR1 to DRR1 copy(B)
Read from DRR1(A)
RBR1 to DRR1 copy(A)
C5
C6
C7
B0
B1
B2
B3
B4
B5
B6
B7
A0
A1
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
A.
CLKR: Internal receive clock
B.
FSR: Internal receive frame-synchronization signal
C.
DR: Data on DR pin
D.
RRDY: Status of receiver ready bit (high is 1)
Figure 15-14. McBSP Reception Signal Activity
The following process describes how data travels from the 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.
In the preceding timing diagram (
), a 1-bit data delay is selected.
3. The McBSP accepts data bits on the DR pin and shifts them into the receive shift registers.
If the word length is 16 bits or smaller, only RSR1 is used. If the word length is larger than 16 bits, RSR2
and RSR1 are used and RSR2 contains the most significant bits. For details on choosing a word length, see
4. When a full word is received, the McBSP copies the contents of the receive shift registers to the receive
buffer registers, provided that RBR1 is not full with previous data.
If the word length is 16 bits or smaller, only RBR1 is used. If the word length is larger than 16 bits, RBR2 and
RBR1 are used and RBR2 contains the most significant bits.
5. The McBSP copies the contents of the receive buffer registers into the data receive registers, provided that
DRR1 is not full with previous data. When DRR1 receives new data, the receiver ready bit (RRDY) is set in
SPCR1. This indicates that received data is ready to be read by the CPU or the DMA controller.
If the word length is 16 bits or smaller, only DRR1 is used. If the word length is larger than 16 bits, DRR2 and
DRR1 are used and DRR2 contains the most significant bits.
If companding is used during the copy (RCOMPAND = 10b or 11b in RCR2), the 8-bit compressed data in
RBR1 is expanded to a left-justified 16-bit value in DRR1. If companding is disabled, the data copied from
RBR[1,2] to DRR[1,2] is justified and bit filled according to the RJUST bits.
6. The CPU or the DMA controller reads the data from the data receive registers. When DRR1 is read, RRDY
is cleared and the next RBR-to-DRR copy is initiated.
Note
If both DRRs are required (word length larger than 16 bits), the CPU or the DMA controller must
read from DRR2 first and then from DRR1. As soon as DRR1 is read, the next RBR-to-DRR copy is
initiated. If DRR2 is not read first, the data in DRR2 is lost.
When activity is not properly timed, errors can occur. See the following topics for more details:
•
Overrun in the Receiver
)
•
Unexpected Receive Frame-Synchronization Pulse
)
15.2.4.6 McBSP Transmission
This section explains the fundamental process of transmission in the McBSP. For details about how to program
the McBSP transmitter, see
.
Multichannel Buffered Serial Port (McBSP)
888
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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