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MT9T111_DG - Rev. B 9/10 EN
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MT9T111: Developer Guide
Output Slew Rate Control
Preliminary
Output Slew Rate Control
System power consumption, noise, and electromagnetic interference (EMI) are reduced
by selecting the optimum slew rate to meet the timing budget.
The MT9T111 output slew rate control register is discussed in the SYSCTL register
section of the MT9T111 data sheet. R0x001E[2:0] controls the D
OUT
[7:0], FRAME_VALID
(FV), LINE_VALID (LV) slew rate. Bits [6:4] control the GPIO[3:0] output slew rate. Bits
[10:8] control the slew rate of PIXCLK, independent of other outputs. Eight slew rates
(code 0–code 7) are selectable. Code 0 is the slowest; code 7 is the fastest. Rise time and
fall time are matched.
S
DATA
and SCLK have no rise time slew rate control. S
DATA
has an open drain output
without an active p-channel transistor. Slew rate control is accomplished by an external
passive resistor.
Figure 7 shows how slew rate is measured.
Figure 7:
Output Slew Rate Defined
Table 12 shows the related registers to program slew rate for output signals. Refer to the
MT9T111 data sheet for more detailed AC/DC electrical specifications.
Table 12:
Slew Rate Control Related Registers
Map
Address
Bits
Descriptions
SYSCTL
0x001E
[10:8]
Controls the output slew rate of PIXCLK signal.
“111” programs the fastest slew rate. Refer to the AD/CD electrical
specification in the data
sheet for the slew rate values. A value of “000” produces the slowest slew rate. The default value
is “100”.
[6:4]
Controls the output slew rate of GPIO signals.
“111” programs the fastest slew rate. Refer to the AC/DC
electrical
specification in the data
sheet for the slew rate values. A default value of “000” produces the slowest slew rate.
[2:0]
Controls the output slew rate of D
OUT
[7:0], FV, and LV signals.
“111” programs the fastest slew rate. Refer to the AC/DC
electrical
specification in the data
sheet for the slew rate values. A default value of “000” produces the slowest slew rate.
Output
90%
10%
90%
10%
TLH
THL
t
t