MB87P2020 Datasheet, PDF (347/356 Pages) Fujitsu Component Limited. – Colour LCD/CRT/TV Controller

Hints and Restrictions
Subject
Testcase
Table 2-11: Overview for Software Reset (incomplete reset)
Description
EMDC: ULB.1, ULB.2 and SDC.6
In case of software reset and anti aliasing (AAF) enabled, data for logical address [Layer 0, Pixel {0,0}] can
be destroyed.
The SwReset command is executed by AAF despite a pending SDRAM access. Therefore layer and pixel
address is reset which causes a wrong address for SDRAM access.
For this restriction two possible workarounds exist which are described in table 2-12.
Table 2-12 gives an overview and a classification about the described problem.
Table 2-12: Overview for Software Reset (AAF)
Subject
Description
Classification
Effects without
workaround
Solution/Workaround
Concerned devices
Testcase
Description
If AAF is enabled SwReset command causes an AAF reset without waiting
for SDC.
HW limitation
If AAF is enabled data for [Layer 0, Pixel {0,0}] can be destroyed.
Workaround 1:
• Do not display [Layer 0, Pixel {0,0}] (either do not use entire layer or do
not use Row 0 and Column 0 for layer 0)
Workaround 2:
• Save physical word at start address of layer 0. This word contains
Pixel {0,0}. Physical access does not need command control.
• Optional: Disable MCU interrupts and wait for GPU frame sync in order
to avoid visible effects on display.
• Send command SwReset (including a NoOp according to table 2-11) to
Jasmine/Lavender
• Restore physical word at start address of layer 0. Pixel {0,0} will be re-
stored in this way.
MB87J2120 (Lavender)
MB87P2020 (Jasmine)
MB87P2020-A (Jasmine redesign)
Code review
2.10 AAF settings double buffering
The command synchronization for AAF settings (register: PPCMD) works not properly. It can happen that
the currently executed command uses the settings from previous command.
In order to avoid this problem a NoOp command should be inserted before AAF settings are manipulated.
A sequence for a drawing command with AAF (turn on before command execution and turn off afterwards)
looks as follows:
GDC_CMD_NOP();
G0PPCMD_EN = 1;
G0AAOE
= ..;
GDC_CMD_Dw...;
GDC_CMD_NOP();
G0PPCMD_EN = 0;
// AAF enable
// AAF init
// Drawing command
// AAF disable
Restrictions
Page 347