SM320F2808-EP Datasheet, PDF (74/118 Pages) Texas Instruments – Digital Signal Processors

SM320F2808-EP, SM320F2806-EP
SM320F2801-EP
Digital Signal Processors
SGLS316A – MARCH 2006 – REVISED FEBRUARY 2007
www.ti.com
The user can select the type of input qualification for each GPIO pin via the GPxQSEL1/2 registers from
four choices:
• Synchronization To SYSCLKOUT Only (GPxQSEL1/2=0,0): This is the default mode of all GPIO pins
at reset and it simply synchronizes the input signal to the system clock (SYSCLKOUT).
• Qualification Using Sampling Window (GPxQSEL1/2=0,1 and 1,0): In this mode the input signal, after
synchronization to the system clock (SYSCLKOUT), is qualified by a specified number of cycles before
the input is allowed to change.
Time between samples
GPyCTRL Reg
GPIOx
SYNC
Qualification
Input Signal
Qualified By 3
or 6 Samples
SYSCLKOUT
GPxQSEL
Number of Samples
Figure 4-17. Qualification Using Sampling Window
• The sampling period is specified by the QUALPRD bits in the GPxCTRL register and is configurable in
groups of 8 signals. It specifies a multiple of SYSCLKOUT cycles for sampling the input signal. The
sampling window is either 3-samples or 6-samples wide and the output is only changed when ALL
samples are the same (all 0s or all 1s) as shown in Figure 4-18 (for 6 sample mode).
• No Synchronization (GPxQSEL1/2=1,1): This mode is used for peripherals where synchronization is
not required (synchronization is performed within the peripheral).
Due to the multi-level multiplexing that is required on the 280x device, there may be cases where a
peripheral input signal can be mapped to more then one GPIO pin. Also, when an input signal is not
selected, the input signal will default to either a 0 or 1 state, depending on the peripheral.
74
Peripherals
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