SPC8106 S-MOS Systems, SPC8106 Datasheet - Page 278

• Manufacturer Part Number: SPC8106
• Description: LCD/CRT VGA CONTROLLER
• Manufacturer: S-MOS Systems

7.0
The purpose of this document is to describe the methodology behind determining the frame rate
on any given panel hooked up to an SPC8106. With the information on how to determine the
frame rate, the reader can then extrapolate the data to adjust the frame rate on any give panel.
(i.e., modification of the Horizontal and Vertical Non-Display periods).
The relation between frame rate (in Hz) and panel geometry is as follows:
FR[Hz] = 3540000.0/(Vertical*Horizontal);
where “Vertical” is the sum of “vertical displayed” and “vertical non-display period” (in lines) and
“horizontal” is the sum of panel “horizontal displayed” and “non-display period” (in character
clocks). For all LCD panels the “horizontal non-display period” is fixed at 14 (decimal) characters.
The values for “Vertical” and “Horizontal” can be determined via the SPC8106FOC CRTC B set
registers.
Constants:
“Horizontal” = CRTCB[01h]+14
“Vertical non-display period” = CRTCB[15h]+2
Single Panels:
“Vertical displayed size” = CRTCB[12h]*2
therefore the frame rate = 3540000.0/((CRTCB[12h]*2+CRTCB[15h]+2)*(CRTCB[01h]+14))
Dual Panels:
“Vertical displayed size” = CRTC_B[12h]*4
therefore the frame rate = 3540000.0/((CRTCB[12h]*4+CRTCB[15h]+2)*(CRTCB[01h]+14))
TFT panels (using LCD like timings):
“Vertical displayed size” is obtained via CRTCB[11h] bits 7 and 6 and CRTCB[12h].
Programming Notes and Examples
SP3-52
1. This formula assumes a 28 MHz clock (3.54MHz = 28.322MHz/8 ).
2. When modifying the frame rate, it is important that the horizontal displayed period is greater
or equal to the horizontal panel size.
ADJUSTING THE SPC8106 FRAME RATE
S-MOS Systems, Inc. • Tel: [phone] • Fax: [phone] • http://www.smos.com
X12-AN-003-02
411-1.0
SPC8106