Texas Instruments OMAP36 Series, Technical Reference Manual

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Public Version
Camera ISP Functional Description
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Translation is enabled by setting the CBUFF_VRFB_CTRL .ENABLEx bit. Software shall not change the
translation configuration or enable/disable the translation while there is active traffic from ISP interface
input port in the translated region (
CBUFF_VRFB_CTRL .BASEx*256M bytes to
CBUFF_VRFB_CTRL .BASEx+1)*256M bytes).
Figure 6-104 shows how the "large" virtual frame buffer seen in the address map of ISP interface input
port is mapped to 4 "small" virtual frames accesses through interface output port.
Figure 6-104. Camera ISP Circular VRFB Buffer Performed Translation
6.4.10.3.2 Camera ISP Circular Buffer Window Management
This section explains the internal address remapping and windows management algorithm. Internally the
module maintains some variables in addition to the configuration registers.
The module manages two circular buffers in parallel. Those are called CBUFF0 and CBUFF1.
Table 6-52. Camera ISP Circular Buffer Internal Variables
Quantity Description
CWx Current window index for buffer x (x = 0, 1).
Possible values are 0 to allowed window count.
The current value can be read using the
CBUFFx_STATUS [11:8] CW register.
NWx Next window index for buffer x (x = 0, 1).
Possible values are 0 to allowed window count.
The current value can be read using the
CBUFFx_STATUS [19:16] NW register.
CPUWx Window in the physical buffer that can be accessed by the CPU.
Possible values are 0 to allowed window count.
The current value can be read using the
CBUFFx_STATUS [3:0] CPUW register.
FCOx Start address, in the virtual space, of the current window.
This is an internal quantity that cannot be accessed by software.
OFFSETy This is an internal quantity that cannot be accessed by software.
y = 0: Address offset used when the current window of buffer 0 is accessed
y = 1: Address offset used when the next window of buffer 0 is accessed
y = 2: Address offset used when the current window of buffer 1 is accessed
y = 3: Address offset used when the next window of buffer 1 is accessed
LEVELy This is an internal quantity that cannot be accessed by software.
y = 0: Amount of data, in bytes, read or written in the current window of buffer 0
y = 1: Amount of data, in bytes, read or written in the next window of buffer 0
y = 2: Amount of data, in bytes, read or written in the current window of buffer 1
y = 3: Amount of data, in bytes, read or written in the next window of buffer 1
6.4.10.3.2.1 Camera ISP Circular Buffer Startup
The status of a circular buffer (CBUFF0 or CBUFF1) is reset when it is disabled. This does not affect the
configuration registers or the
CBUFF_IRQSTATUS register. Table 6-53 shows the internal state after
reset.
Table 6-53. Camera ISP Circular Buffer Internal State After Reset
Quantity Description
CWx 0
NWx 1
1240Camera Image Signal Processor SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated