General
Review and verify the
following for the custom schematic design:
- Reviewed
above "Common checklist for all
sections" section of the user's guide.
- GPMC
interface configuration and recommended
connections.
- Connection of series resistor and pulldown for
GPMC0 clock.
- IO level
compatibility between processor and attached device.
- Connection of required pulls for IOs.
- Supported
address and data range.
- Connection of open-drain output type signal active
high ready and active low busy (R/B#) outputs from
the NAND flash.
- Boot mode
inputs configured for alternate function (GPMC
interface).
- GPMC
interface timing required versus calculated and
effect of layout on the timing. Timing and IO load
calculation performed when connecting to multiple
devices in Async mode.
Schematic
Review
Follow the below list for
the custom schematic design:
- GPMC
interface configuration and recommended connections.
Connection of GPMC memory NAND/ NOR, address and
data signals - multiplexed or non-multiplexed,
synchronous or asynchronous, data bit width as per
the processor-specific TRM.
- Supported
address and data range (IOs pinned out for the
processor as mentioned in the processor-specific
data sheet).
- IO level
compatibility between processor and attached device.
The attached device IO supply and IO supply for IO
group VDDSHV3 referenced to (powered by) the GPMC
interface signals are connected to the same supply
source.
- The
recommended pulls (47kΩ) are provided for the
interface signals that can float (to prevent the
attached device inputs from floating until driven by
the host).
- The
recommendation is to provision for external pullups
on GPMC0_CSn0-3 (depending on the configuration) to
prevent the attached device inputs from floating
until driven by the host.
- Series
resistor (0Ω) provision for GPMC0_CLK (close to
processor clock output pin to control possible
signal reflections) and external pulldown (10kΩ) for
GPMC0_CLK (close to attached device clock input pin)
to hold the attached device in low state (there are
cases where the clock is stopped or paused in a low
logic state and the pulldown option is consistent
with this logic state).
- Supply
rails connected to the IO supply for IO group
VDDSHV3 referenced to (powered by) GPMC0 peripheral
and attached device IO supply are sourced from the
same source and follow the ROC.
- Open-drain output type signal active high ready and
active low busy (R/B#) outputs from the NAND flash
are connected to the GPMC0_WAIT0 and GPMC0_WAIT1
signals (depending on the configuration). The
recommendation is to provide the pullup (commonly
used value 10kΩ) close to the attached device.
- Boot mode
inputs configured for alternate function (GPMC
interface) through a 0Ω to be able to isolate to
check boot mode functionality.
- Implementation of reset logic when used for boot. The
recommendation is to implement the attached device
(memory) reset using a 2-input ANDing logic.
Processor GPIO is connected as one of the input to
the AND gate with provision for pullup (10kΩ or
47kΩ) (to support boot) near to the ANDing logic AND
gate input and provision for 0Ω to isolate the GPIO
output for testing or debug. The other input to the
AND gate is the MAIN domain warm reset status output
(RESETSTATz).