SX and VGA noise

Magister

Hi.

I am working on a simple vga controller using the SX28, which is running at 50mhz using an oscillator. The Sx does not directly control the colors as i have attached a 32kx8 ram which store the pixel information, the SX only controls the H and V Sync directly. The whole assembly is on a solder less breadboard using 2 buffers, 2 latches and counter for address. the problem is that no matter how its connected, there is noise on the display, it shows as vertical bars that are fade but visible. Its generated from the clock since if I use a 20mhz oscillator the bars are more spread out and less visible. Also connecting the power supply of the oscillator to a different point on the board makes the bars more visible or less depending on the location but I was unable to eliminate them does any one have an idea how to get rid of it? Any filtering needed? or suggestion ?

Thank you

Janusz.

Draft sketch of the schematic


OSC -> SX28 -> Buffer

---

I/0

---

>Ram

---

I/0

---

>Buffer

---

>Display
^^
-> Latch-Lo ---> Counter_lo

---

| | Address
-> Latch-Hi ----> Counter_hi

---

Magister

Ok I guess am not clear, what the problem is that there is interference on the display (LCD) could a some kind of filter work to filter the frequencies getting through? maybe high or low pass filter?

PJMonty

Janusz,

Why are you posting your message asking for help with an SX in the "Sandbox"? Does it not make more sense to you to post in the forum called "SX Microcontrollers, SX/B Compiler and SX-Key Tool" instead?

Thanks,
PeterM

Magister

At first I was not sure if this was the right form, now i see. Thank you I will post in the SX form.