15.9 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
15.9.1 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.
15.9.2 Resetting and Initializing McBSP
15.9.2.1 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.
Table 15-70. Reset State of Each McBSP Pin
Pin
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
(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.
15.9.2.2 Device Reset, McBSP Reset, and Sample Rate Generator Reset
When the McBSP is reset in either of the above two ways, the machine is reset to its initial state, including reset
of all counters and status bits. The receive status bits include RFULL, RRDY, and RSYNCERR. The transmit
status bits include XEMPTY, XRDY, and XSYNCERR.
• Device reset. When the whole DSP is reset (XRS signal is driven low), all McBSP pins are in GPIO mode.
When the device is pulled out of reset, the clock to the McBSP modules remains disabled.
Multichannel Buffered Serial Port (McBSP)
954
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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