lm2502sm National Semiconductor Corporation, lm2502sm Datasheet - Page 24

• Manufacturer Part Number: lm2502sm
• Description: Mobile Pixel Link Mpl Display Interface Serializer And Deserializer
• Manufacturer: National Semiconductor Corporation

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Application Information
RGB565 APPLICATION
The LM2502 chipset may also be configured for a RGB565
application. This is also known as a "buffer-less" or "dumb"
display application. In this configuration 16 color bits (R[4:0],
G[5:0], B[4:0]), Pixel Clock (PCLK) and two control bits (VS
and HS) are supported. An external invertor is also required.
To configure for the RGB565 mode, the i80 mode must be
selected. The Pixel clock should be connected to both the
CLK input and the WR* pins on the Master. The PLL_CON
pins should be configured for a 6X mode, as it takes 5 MC
cycles to transfer the RGB data, and the 6X setting will
provide a 50% output PCLK from the Slave device. The 50%
duty cycle PCLK is created by the WR* signal which pulses
low for 3 MC cycles and is high for 2 MC cycles and an idle
QVGA Example - For a QVGA display (320 by 240), with 16
bits of color depth and 60 frames per second, a net band-
width requirement is 73.728 Mbps. Maximum transfer rate
FIGURE 19. Display Interface Application
(Continued)
FIGURE 20. RGB565 Application
24
MC cycle. See Figure 20 for details. Support is provided for
PCLKs in the 3 to 25 MHz range. PLLCON setting of X8 is
also possible, however, the Slave output PCLK (WR*) will
have some duty cycle distortion (37.5%).
Slower PCLK rates maybe supported if a higher frequency
multiple of the PCLK is available. For example, if a 2MHz
PCLK is required, then a 6MHz CLK (freq locked, not phase)
may be applied to the MST CLK input and the 2MHz PCLK
to the MST WR* signal input. The PLLCON setting should be
selected as 2X (PLLCON[2:0] = 000’b). Once again 5 MC
cycles are required to transfer the pixel data, and the WR*
(PCLK) will be 50% duty cycle. The applied CLK and
PLLCON should be selected such that is creates a 6X
multiple on MC to ensure a 50% duty cycle.
for the LM2502 chipset is 245 Mbps (307 Mbps raw - in-
cludes overhead), thus there is adequate bandwidth for this
application and even larger resolution displays.
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