ADV8005 Hardware Reference Manual
UG-707
4.2.5.2.
OSD Color Space
Bitmap images as well as external OSDs are passed to the OSD core in 8-bit RGB format. However, all video processing in the
place in YCbCr. The OSD core features a CSC to enable conversion of the OSD data from RGB to YCbCr. The OSD core CSC can convert into
either full of limited range YCbCr.
4.2.6.
OSD Timers
OSD supports up to eight hardware timers. One of these timers (user-selectable in the OSD firmware) is used by the
OSDTimer
component of
Blimp OSD
, which can be inserted within any OSD design (consult the
Blimp OSD
manual for a detailed description of how to do
this).
Blimp OSD
will automatically handle a number of OSD timers and will map all of them to one hardware timer. If the OSD design flow with
the
Blimp OSD
tool is followed, the user does not need to know any low-level details about the timers. However, since they can also be used as
general purpose system timers, its low-level functionality will be described in this section. Note that the HW timer being used by
Blimp OSD
(user-selectable as mentioned) will not be available to be used as general purpose timer.
Any of these eight timers can trigger an interrupt on the INT0 pin. This interrupt can then be handled by the MCU, and the timer which
generated it can be found out by polling the timer registers.
These timers can be configured through the Timer register map. This map is only accessible through the SPI slave interface (address 0x0B). For
more information on the SPI slave interface, refer to Section
. The registers used to configure the timers are described below.
sys_clock_freq[23:0]
, SPI Device Address 0x0B (TIMER),
Address 0x00[7:0]; Address 0x01[7:0]; Address 0x02[7:0]
System clock frequency, unit is KHz, the default value is 157.5 MHz.
Function
sys_clock_freq[23:0]
Description
0x02673C
Default
0xXXXXXX
System Clock Frequency
This register is used to generate a 1 KHz pulse, which all eight timers are based on to measure a 1 ms interval. If the system clock frequency is
changed, this register can be changed to guarantee the 1 KHz accuracy. It is also possible to modify this register if a smaller time interval than
1ms needs to be measured.
For example:
The default value of sys_clock_freq is 0x0278D0, that is, 162000 (162 MHz).
If it is changed to 16200, the minimum interval will be 0.1 ms.
If it is changed to 1620, the minimum interval will be 0.01ms.
timer1_enable
, SPI Device Address 0x0B (TIMER),
Address 0x03[0]
Timer 1 Enable
Function
timer1_enable
Description
0
Disables
1
Enables
Once the timer is enabled, disabling this bit will stop the counting, and it will be resumed when enabling back this bit.
Note that the rest of the bits within this register perform the same operation as for timer1 but for the other seven timers (i.e. bit[1] controls
timer2, bit[2] controls timer3, etc.); they are not included here for readability reasons.
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