ADV
ANCEINFORMA
TION
GPIO Signal
1
Sampling Window
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
SYSCLK
(A)
GPxQSELn = 1,0 (6 samples)
(D)
Output From
Qualifier
QUALPRD = 1
(SYSCLK/2)
t
w(IQSW)
t
w(SP)
(SYSCLK cycle * 2 * QUALPRD) * 5
(C)
Sampling Period determined
by GPxCTRL[QUALPRD]
(B)
TMS320F28377S, TMS320F28376S, TMS320F28375S, TMS320F28374S
SPRS881A – AUGUST 2014 – REVISED JUNE 2015
5.7.6.2
GPIO - Input Timing
Table 5-23. General-Purpose Input Timing Requirements
MIN
MAX
UNIT
QUALPRD = 0
1t
c(SYSCLK)
cycles
t
w(SP)
Sampling period
QUALPRD
≠
0
2t
c(SYSCLK)
* QUALPRD
cycles
t
w(IQSW)
Input qualifier sampling window
t
w(SP)
* (n
(1)
– 1)
cycles
Synchronous mode
2t
c(SYSCLK)
cycles
t
w(GPI)
(2)
Pulse duration, GPIO low/high
With input qualifier
t
w(IQSW)
+ t
w(SP)
+ 1t
c(SYSCLK)
cycles
(1)
"n" represents the number of qualification samples as defined by GPxQSELn register.
(2)
For t
w(GPI)
, pulse width is measured from V
IL
to V
IL
for an active low signal and V
IH
to V
IH
for an active high signal.
A.
This glitch will be ignored by the input qualifier. The QUALPRD bit field specifies the qualification sampling period. It
can vary from 00 to 0xFF. If QUALPRD = 00, then the sampling period is 1 SYSCLK cycle. For any other value "n",
the qualification sampling period in 2n SYSCLK cycles (that is, at every 2n SYSCLK cycles, the GPIO pin will be
sampled).
B.
The qualification period selected via the GPxCTRL register applies to groups of 8 GPIO pins.
C.
The qualification block can take either three or six samples. The GPxQSELn Register selects which sample mode is
used.
D.
In the example shown, for the qualifier to detect the change, the input should be stable for 10 SYSCLK cycles or
greater. In other words, the inputs should be stable for (5 x QUALPRD x 2) SYSCLK cycles. This would ensure
5 sampling periods for detection to occur. Because external signals are driven asynchronously, an 13-SYSCLK-wide
pulse ensures reliable recognition.
Figure 5-10. Sampling Mode
70
Specifications
Copyright © 2014–2015, Texas Instruments Incorporated
Product Folder Links:
