VmodCAM Reference Manual

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A register read consists of:

•

start condition

•

8-bit device address (0x78 for the

MT9D112) + acknowledge bit

•

upper byte of 16-bit register address +

acknowledge bit

•

lower byte of register address +

acknowledge bit

•

start condition

•

8-bit device address (0x79 for the

MT9D112) + acknowledge bit

•

upper byte of the 16-bit data +

acknowledge bit

•

lower data byte + no-acknowledge bit

•

stop condition.

There are two types of configuration controls,

hardware registers and driver variables. The

hardware registers usually control the sensor

and some other sub-systems, while the driver

variables sequence the on-chip

microprocessor. These two types of controls

are accessed differently.

Hardware registers are two-wire accessible,

meaning their address can be used directly in

the register address phase of the two-wire

transfer. Hardware registers are referred to by

their address. For example, R[0x3000] refers

to the register located at address 0x3000.

Driver variables can be accessed via two

hardware registers, R[0x338C] and R[0x3390].

To access a variable, its address first needs to

be written to R[0x338C], which is a standard

two-wire register write. Then, reading register

R[0x3390] reads the variable and writes a

value to it, thus setting the variable to that

value. Driver variables are referred to by their

address. For example, V[0x2797] refers to the

driver variable located at address 0x2797.

Configuration

The cameras start up with their registers set to

default values. This also means they are in

standby. To acquire images from the cameras,

both have to be initialized properly. As the

power-on and reset sequences show, the

camera needs certain signals set and a

running MCLK before the two-wire interface is

enabled.

Once the necessary number of MCLK cycles

are provided, the following registers/variables

need to be read/written.

Identify the camera:

To verify that the camera is working, read

R[0x3000] to return 0x1580, which is the

device ID of the camera.

Reset the MCU:

1. R[0x3386] = 0x0501

2. R[0x3386] = 0x0500; release from reset

Set the PLL:

1. R[0x3214] = 0x0D85; this sets the slew

rate of the output pins

2. R[0x341E] = 0x8F0B; power-down and

bypass PLL; if you want to use MCLK

as the pixel clock, skip steps 3-5.

3. R[0x341C][13:8] = N

R[0x341C][7:0] = M;

Where PCLK = MCLK * M / (N+1) / 8.

For example, to obtain a pixel clock of

80MHz (maximum) from an MCLK of

24MHz, set M=80, N=2.

4. R[0x341E] = 0x8F09; power up PLL,

wait 1ms for the PLL to stabilize

5. R[0x341E] = 0x8F08; use PLL clock

instead of MCLK

Wake up from standby:

1. R[0x3202] = 0x0008

Insert image parameters:

You can change the image parameters to suit

your project. See the Image Configuration

Example below to insert an image parameter

configuration sequence.