I.MX27 Datasheet, PDF (51/148 Pages) Freescale Semiconductor, Inc – Multimedia Applications Processor

Electrical Characteristics
Number
1
2
3
4
5
6
7
Table 21. Gated Clock Mode Timing Parameters
Parameter
csi_vsync to csi_hsync
csi_hsync to csi_pixclk
csi_d setup time
csi_d hold time
csi_pixclk high time
csi_pixclk low time
csi_pixclk frequency
Minimum
9*THCLK
3
1
1
THCLK
THCLK
0
Maximum
—
(Tp/2)-3
—
—
—
—
HCLK/2
Unit
ns
ns
ns
ns
ns
ns
MHz
HCLK = AHB System Clock, THCLK = Period for HCLK, Tp = Period of CSI_PIXCLK
The limitation on pixel clock rise time/fall time is not specified. It should be calculated from the hold
time and setup time based on the following assumptions:
Rising-edge latch data:
max rise time allowed = (positive duty cycle—hold time)
max fall time allowed = (negative duty cycle—setup time)
In most of case, duty cycle is 50/50, therefore:
max rise time = (period/2—hold time)
max fall time = (period/2—setup time)
For example: Given pixel clock period = 10 ns, duty cycle = 50/50, hold time = 1 ns, setup time = 1 ns.
positive duty cycle = 10/2 = 5 ns
max rise time allowed = 5 –1 = 4 ns
negative duty cycle = 10/2 = 5 ns
max fall time allowed = 5 –1 = 4 ns
Falling-edge latch data:
max fall time allowed = (negative duty cycle—hold time)
max rise time allowed = (positive duty cycle—setup time)
4.2.5.2 Non-Gated Clock Mode Timing
In non-gated mode only, the VSYNC, and PIXCLK signals are used; the HSYNC signal is ignored. Figure
3 and Figure 4 show the different clock edge timing of CSI and Sensor in Non-Gated Mode. Table 3 is the
parameter value. Figure 11 and Figure 12 show the non-gated clock mode timings of CSI, and Table 22
lists the timing parameters.
i.MX27 and i.MX27L Data Sheet, Rev. 1.5
Freescale Semiconductor
51