MB87P2020 Datasheet, PDF (336/356 Pages) Fujitsu Component Limited. – Colour LCD/CRT/TV Controller

MB87J2120, MB87P2020-A Hardware Manual
Subject
Effects without
workaround
Solution/Workaround
Concerned devices
Testcase
Table 1-5: Overview for PP double buffering
Description
READINIT_RCR=0: read internal register (reset value)
READINIT_RCR=1: read configuration register
Be careful with Read-Modify-Write accesses; use READINIT_RCR=1 in
this case.
No workaround required.
MB87J2120 (Lavender)
MB87P2020 (Jasmine)
MB87P2020-A (Jasmine redesign)
EMDC: SDC.LOG2PHY
1.6 Robustness of ULB_RDY signal
Disturbances at external bus interface (ULB interface) can cause the ULB_RDY pin to stay in active state
(logic ’0’) during a bus read access. This stops a MB91360 series MCU completely so that no further com-
mands will be executed (blocking of external bus). Only a MCU watchdog can reset the system.
To avoid this problem the PCB layout should be done very carefully especially for the signals ULB_CS,
ULB_RDX and ULB_WRX[3:0]. The following hints may help:
• Place MCU and Lavender as close as possible together on PCB.
• Use separate ground plane on PCB in order to avoid interferences with other signals.
• Place SDRAM and Lavender as close as possible together in order to avoid interferences from SDRAM
interface to ULB interface
The interface circuit has been redesigned for Jasmine so that this problem should not occur with this device.
Additionally for Jasmine an ULB_RDY timeout has been added so that a ’hanging’ ULB_RDY can not
block the hole system. See hardware manual for further details.
Table 1-6 gives an overview and a classification about the described problem.
Table 1-6: Overview for ULB_RDY robustness
Subject
Description
Classification
Effects without
workaround
Solution/Workaround
Concerned devices
Testcase
Description
ULB_RDY signal may hang as a result of signal distortions on PCB.
Hint
A hanging ULB_RDY pin blocks the command execution of a MB91360
series MCU.
Keep special attention to PCB layout.
This problem should not occur with Jasmine. Additionally a timeout for
ULB_RDY has been added.
MB87J2120 (Lavender)
fixed for MB87P2020 (Jasmine)
fixed for MB87P2020-A (Jasmine redesign)
Every testcase.
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