LCD Controller Registers
11-37
LCD Controller
Vertical Back Porch (VBP)
The 8-bit vertical back porch (VBP) field is used to specify the number of hori-
zontal synchronizations (line clocks) to insert at the beginning of each frame.
The VBP count starts just after the VSYNC signal for the previous frame has
been negated for active mode or the extra horizontal synchronizations have
been inserted as specified by the VSW bit field in passive mode. After this has
occurred, the value in VBP is used to count the number of horizontal synchro-
nization periods to insert before starting to output pixels in the next frame. VBP
generates 0 – 255 extra line clock cycles.
Figure 11–15 and Figure 11–16 show the use of LCD timing register 1 control
fields for active and passive displays, respectively.
Vertical Front Porch (VFP)
The 8-bit vertical front porch (VFP) field is used to specify the number of hori-
zontal synchronizations (line clocks) to insert at the end of each frame. Once
a complete frame of pixels is transmitted to the LCD display, the value in VFP
is used to count the number of horizontal synchronization periods to wait. After
the count has elapsed, the VSYNC (LCD.VS) signal is pulsed in active mode,
or extra horizontal synchronizations are inserted as specified by the VSW bit
field in passive mode. VFP generates 0 – 255 line clock cycles.
Note:
The line clock pin LCD.HS transitions during the generation of the VFP line
clock periods.
Figure 11–15.
Active Mode End of Frame Timing
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
VFP=1
LCD.VS
LCD.P
LCD.HS
VSW=1
VBP=2
First
line of
frame
n+1
Second
line of
frame
n+1
Last
line of
frame
n