Datasheet
should be in the range of the configured PRATE
range, and the following relationship formula must
be met:
Serial Word Length x Pixel Clock = Serial
Data Rate ≤ 840Mbps
It is preferred to select the pixel clock frequency
before the clock is enabled.
14) To select a different UART speed, change the cam-
era UART speed first and then go to the ECU
Control tab sheet to change the ECU UART speed
accordingly. Ensure that t
STO
and t
ETO
values are
set correctly in order for the UART speed to work
properly. The MAX9258A REG07 FAST bit and
MAX9257A REG08 FAST bit should be configured
correctly before going to the never come back
operation.
15) Press the Disable PCLK_IN/HSYNC_IN/VSYNC_IN
button to disable the video clock inputs to the
MAX9257A. Check that the D1 green LED is turned
off (MAX9258A LOCK pin stays low) and that the
control channel is available indefinitely (MAX9258A
CCEN pin stays high).
16) Press the Enable PCLK_IN/HSYNC_IN/VSYNC_IN
button again to enable the video clock inputs to the
MAX9257A. Check that the D1 green LED lights up
again.
UART with Finite CTO Operation
If t
CTO
< t
ETO
then the MAX9257A and the MAX9258A
registers can be accessed and UART communication
with the camera in bypass mode is possible.
1) Start the program or press the Reset the EVKIT
button on the ECU Control tab sheet (Figure 3).
2) If MAX9257A REM is set to high (JU25 shunt is set
across pins 1-2), then press the ECU Wakes Up
MAX9257A button on the ECU Control tab sheet. If
MAX9257A REM is set to low (JU25 shunt is set
across pins 2-3), then skip this step.
3) Navigate to the Deserializer MAX9258A tab sheet
(Figure 4). Press the Read MAX9258A & 9257A
button to refresh the current register values on the
GUI.
4) Keep the four Write Both 9258A&9257A checkbox-
es checked.
5) Set t
STO
and t
ETO
on both the MAX9258A and
MAX9257A to desired values. Note that the t
STO
and t
ETO
times are based on pixel clock (PCLK_IN)
time. For example, if PCLK_IN is 30MHz, set
STODIV to 1024 and STOCNT to 0, t
STO
= (1024 x
1/30)µs ≈ 34µs. Set ETODIV to 1024 and ETOCNT
to 9, t
ETO
= (1024 x 10/30)µs ≈ 340µs.
6) Set t
CTO
on both MAX9258A and MAX9257A to
desired values. Note that the t
CTO
time is based on
the UART bit time. For example, if the UART speed
is 400kbps, set CTO to 64, t
CTO
= (64 x 2.5)µs =
140 µs.
7) Set other MAX9258A registers as desired.
8) Navigate to the Serializer MAX9257A tab sheet
(Figure 5). Select enable in the SEREN drop-down
list within the Reg04 controls if it is not enabled.
9) Select enable in the INTEN drop-down list within the
Reg08 controls on the Serializer MAX9257A tab
sheet. INTEN is changed in both MAX9258A and
MAX9257A when the INTEN drop-down list is
changed on either tab sheet.
10) Press the Read button to read back the contents of
Reg08. Ensure that the INTEN drop-down list dis-
plays disabled because CTO expired by the time
the read operation executed and STO/ETO are not
counting yet since the pixel clock is not activated.
11) Navigate to the Camera Control tab sheet (Figure
6). On this tab sheet, all ECU commands to the
camera follow this order in one control-channel ses-
sion:
a) SYNC frame
b) Set MAX9258A INTEN to 1
c) Wait for 15 UART bit times
d) Set MAX9257A INTEN to 1
e) ECU command to the camera
After every command, CTO expires first because of
t
CTO
< t
ETO.
This resets INTEN on both MAX9258A
and MAX9257A to 0 so that they become accessi-
ble again when the next control channel is avail-
able.
12) Press the Turn On D4, Turn Off D4, Fast Blink D4,
and Slow Blink D4 buttons to verify that the ECU
communicates to the camera properly.
13) Press the Enable PCLK_IN/HSYNC_IN/VSYNC_IN
button to enable the pixel clock, the horizontal syn-
chronization clock, and the vertical synchronization
clock. The frequencies are displayed in the
Onboard PCLK_IN, HSYNC_IN, VSYNC_IN Status
group box.
14) Use an oscilloscope to check that CCEN is toggling
and the D1 green LED is lit (MAX9258A LOCK pin is
asserted high).
Evaluates: MAX9257A/MAX9258A
MAX9257A/MAX9258A Evaluation Kit
_______________________________________________________________________________________ 9