Mcbsp Overview; Resetting The Serial Port: Rrst, Xrst, Grst, And Reset; Reset State Of Mcbsp Pins - Texas Instruments TMS320C6000 Reference Manual

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McBSP Overview

3.1

Resetting the Serial Port: RRST, XRST, GRST, and RESET

Table 3.

Reset State of McBSP Pins

Pin Direction
DR I
CLKR I/O/Z
FSR I/O/Z
CLKS I
DX O/Z
CLKX I/O/Z
FSX I/O/Z
CLKS I
SPRU580C
As shown in Figure 1, the receive operation is triple-buffered and the transmit
operation is double-buffered. Receive data arrives on the DR and is shifted into
the RSR. Once a full element (8, 12, 16, 20, 24, or 32 bits) is received, the RSR
is copied to the receive buffer register (RBR) only if the RBR is not full. The
RBR is then copied to DRR unless the DRR has not been read by the CPU or
the DMA/EDMA controller.
The CPU or the DMA/EDMA controller writes transmit data to DXR. If there is
no data in XSR, the value in DXR is copied to XSR. Otherwise, the DXR is
copied to XSR when the last bit of data is shifted out on the DX. After transmit
frame synchronization, XSR begins shifting out the transmit data on the DX.
The serial port can be reset in the following two ways:
Device reset (RESET pin is low) places the receiver, the transmitter, and
-
the sample rate generator in reset. When the device reset is removed
(RESET = 1), FRST = GRST = RRST = XRST = 0, keeping the entire
serial port in the reset state.
The serial port transmitter and receiver can be independently reset by the
-
XRST and RRST bits in the serial port control register (SPCR). The sample
rate generator is reset by the GRST bit in SPCR.
Table 3 shows the state of the McBSP pins when the serial port is reset by
these methods.
Device Reset
(RESET = 0)
McBSP Reset
Receiver Reset (RRST = 0 and GRST = 1)
Input Input
Input Known state if input; CLKR if output
Input Known state if input; FSRP(inactive state) if output
Input Input
Transmitter Reset (XRST = 0 and GRST = 1)
High impedance High impedance
Input Known state if input; CLKX if output
Input Known state if input; FSXP(inactive state) if output
Input Input
Multichannel Buffered Serial Port (McBSP)
McBSP Overview
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