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Architecture
1235
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Multichannel Buffered Serial Port (McBSP)
25.2.11.2 Hardware Reset Considerations
When the McBSP is reset due to device reset, the entire serial port (including the transmitter, receiver,
and the sample rate generator) is reset. All input-only pins and 3-state pins should be in a known state.
The output-only pin, DX, is in the high-impedance state. When the device is pulled out of reset, the serial
port remains in the reset condition (RRST = XRST = FRST = GRST = 0 in SPCR).
25.2.12 McBSP Initialization Procedure
The McBSP initialization procedure varies depending on the specific system setup.
provides a general initialization sequence.
The transmitter and the receiver of the McBSP can operate independently from each other. Therefore,
they can be placed in or taken out of reset individually by modifying only the desired bit in the registers
without disrupting the other portion. The steps in the following sections discuss the initialization procedure
for taking both the transmitter and the receiver out of reset. To initialize only one portion, configure only
the portion desired.
The McBSP internal sample rate generator and internal frame sync generator are shared between the
transmitter and the receiver.
and
describe their usage base upon the clock and
frame sync configurations of the receiver and transmitter, respectively.
Table 25-19. Receiver Clock and Frame Configurations
CLKR Source
FSR Source
Comment on Configuration
Internal
Internal
The McBSP internal sample rate generator and internal frame sync generator are used by the
receiver.
External
Internal
The McBSP internal sample rate generator and internal frame sync generator are used by the
receiver.
Internal
External
The McBSP internal sample rate generator is used but the internal frame sync generator is
not used by the receiver.
External
External
The McBSP internal sample rate generator and internal frame sync generator are not used by
the receiver.
Table 25-20. Transmitter Clock and Frame Configurations
CLKX Source
FSX Source
Comment on Configuration
Internal
Internal
The McBSP internal sample rate generator is used by the transmitter. The transmitter can
generate frame sync FSX in one of two ways. First, it can generate FSX by using the internal
frame sync generator (FSGM = 1). Alternatively, it can generate FSX upon each DXR-to-XSR
copy (FSGM = 0). In this case, the internal frame sync generator can be kept in reset
(FRST = 0) if it is not used by the receiver. You can follow the general initialization sequence
in
External
Internal
The McBSP internal sample rate generator and internal frame sync generator are not used by
the transmitter. This configuration is only valid with FSGM = 0 where the McBSP transmitter
generates FSX upon each DXR-to-XSR copy. You can follow the general initialization
sequence in
Internal
External
The McBSP internal sample rate generator is used by the transmitter but the internal frame
sync generator is not.
External
External
The McBSP internal sample rate generator and internal frame sync generator are not used by
the transmitter.