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FSR
detection
Frame pulse
FWID
CLKG
FSG
Pulse
Frame
FPER
CLKGDV
CLKSRG
÷
÷
CLKSP
CLKS
McBSP
internal
clock
SCLKME, CLKSM
synchronization
and clock
GSYNC
0,0
0,1
1,0
1,1
CLKRP
CLKR pin
CLKXP
CLKX pin
Architecture
1198
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Multichannel Buffered Serial Port (McBSP)
25.2.5.2 Sample Rate Generator Clocking and Framing
The sample rate generator is composed of a 3-stage clock divider that provides a programmable data
clock (CLKG) and framing signal (FSG), as shown in
. CLKG and FSG are McBSP internal
signals that can be programmed to drive receive and/or transmit clocking, CLK(R/X), and framing,
FS(R/X). The sample rate generator can be programmed to be driven by an internal clock source or an
internal clock derived from an external clock source.
The sample rate generator is not used when CLKX, FSX, CLKR, and FSR are driven by an external
source. Therefore, the GRST bit in the serial port control register (SPCR) does not need to be enabled
(GRST = 1) for this setup. The three stages of the sample rate generator circuit compute:
•
Clock divide-down (CLKGDV): The number of input clocks per data bit clock
•
Frame period (FPER): The frame period in data bit clocks
•
Frame width (FWID): The width of an active frame pulse in data bit clocks
In addition, a frame pulse detection and clock synchronization module allows synchronization of the clock
divide-down with an incoming frame pulse. The operation of the sample rate generator during device reset
is described in
Figure 25-5. Sample Rate Generator Block Diagram