A2
D(R/X)
FS(R/X)
C6
C7
B0
B2
B3
B5
B6
B7
A0
A1
B1
CLK(R/X)
B4
Preliminary
Architecture
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11.2.1.3.4 Detecting Frame–Synchronization Pulses, Even in Reset State
The McBSP can generate receive and transmit interrupts to the CPU to indicate specific events in the
McBSP. To facilitate detection of frame synchronization, these interrupts can be sent in response to
frame–synchronization pulses. Unlike other serial port interrupt modes, this mode can operate while the
associated portion of the serial port is in reset (such as activating RINT when the receiver is in reset). In
this case, FSRM/FSXM and FSRP/FSXP still select the appropriate source and polarity of frame
synchronization. Thus, even when the serial port is in the reset state, these signals are synchronized to
the CPU clock and then sent to the CPU in the form of RINT and XINT at the point at which they feed
the receiver and transmitter of the serial port. Consequently, a new frame–synchronization pulse can be
detected, and after this occurs the CPU can take the serial port out of reset safely.
11.2.1.3.5 Ignoring Frame–Synchronization Pulses
The McBSP ignores transmit and/or receive frame–synchronization pulses while the frame transfer has
been already started by a previous frame–synchronization pulse (unexpected frame–synchronization
pulses). The McBSP does not support features like re-transmit or re-receive of an erroneous frame or
word. The receiver or transmitter ignores frame–synchronization pulses until the desired frame length or
number of words is reached. For more details on unexpected frame–synchronization pulses, see
and
.
11.2.1.3.6 Frame Frequency
The frame frequency is determined by the period between frame–synchronization pulses and is defined
as shown in the following equation:
Frame frequency = Clock frequency / (Number of clock cycles between frame – Sync pulses)
The frame frequency can be increased by decreasing the time between frame–synchronization pulses
(limited only by the number of bits per frame). As the frame transmit frequency increases, the inactivity
period between the data packets for adjacent transfers decreases to zero.
11.2.1.3.7 Maximum Frame Frequency
The minimum number of clock cycles between frame synchronization pulses is equal to the number of
bits transferred per frame. The maximum frame frequency is defined as shown in the following
equation:
Maximum frame frequency = Clock frequency / Number of bits per frame
shows the McBSP operating at maximum packet frequency. At maximum packet frequency,
the data bits in consecutive packets are transmitted contiguously with no inactivity between bits.
Figure 11-4. McBSP Operating at Maximum Packet Frequency
If there is a 1–bit data delay as shown in this figure, the frame–synchronization pulse overlaps the last
bit transmitted in the previous frame. Effectively, this permits a continuous stream of data, back-to-back
transfers.
For XDATDLY = 0 (0-bit data delay), the first bit of data is transmitted asynchronously to the internal
transmit clock signal (CLKX).
1128
Multichannel Buffered Serial Port (McBSP)
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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