Emulation and Reset Considerations
1114
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Multichannel Buffered Serial Port (McBSP)
15.10 Emulation and Reset Considerations
This section covers the following topics:
•
How to program McBSP response to a breakpoint in the high-level language debugger (see
)
•
How to reset and initialize the various parts of the McBSP (see
)
15.10.1 McBSP Emulation Mode
FREE and SOFT are special emulation bits in SPCR2 that determine the state of the McBSP when a
breakpoint is encountered in the high-level language debugger. If FREE = 1, the clock continues to run
upon a software breakpoint and data is still shifted out. When FREE = 1, the SOFT bit is a
don't care.
If FREE = 0, the SOFT bit takes effect. If SOFT = 0 when breakpoint occurs, the clock stops immediately,
aborting a transmission. If SOFT = 1 and a breakpoint occurs while transmission is in progress, the
transmission continues until completion of the transfer and then the clock halts. These options are listed in
.
The McBSP receiver functions in a similar fashion. If a mode other than the immediate stop mode (SOFT
= FREE = 0) is chosen, the receiver continues running and an overrun error is possible.
Table 15-69. McBSP Emulation Modes Selectable with FREE and SOFT Bits of SPCR2
FREE
SOFT
McBSP Emulation Mode
0
0
Immediate stop mode (reset condition)
The transmitter or receiver stops immediately in response to a breakpoint.
0
1
Soft stop mode
When a breakpoint occurs, the transmitter stops after completion of the current word. The receiver is
not affected.
1
0 or 1
Free run mode
The transmitter and receiver continue to run when a breakpoint occurs.
15.10.2 Resetting and Initializing McBSP
15.10.2.1 McBSP Pin States: DSP Reset Versus Receiver/Transmitter Reset
shows the state of McBSP pins when the serial port is reset due to direct receiver or
transmitter reset on the device.
(1)
In Possible State(s) column, I = Input, O = Output, Z = High impedance. In the 28x family, at device reset, all I/Os default to
GPIO function and generally as inputs.
Table 15-70. Reset State of Each McBSP Pin
Pin
Possible State(s)
(1)
State Forced by Device
Reset
State Forced by
Receiver/Transmitter Reset
Receiver reset (RRST = 0 and GRST = 1)
MDRx
I
GPIO-input
Input
MCLKRx
I/O/Z
GPIO-input
Known state if input; MCLKR running if output
MFSRx
I/O/Z
GPIO-input
Known state if input; FSRP inactive state if output
Transmitter reset (XRST = 0 and GRST = 1)
MDXx
O/Z
GPIO Input
High impedance
MCLKXx
I/O/Z
GPIO-input
Known state if input; CLKX running if output
MFSXx
I/O/Z
GPIO-input
Known state if input; FSXP inactive state if output