Functional Blocks Description
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SPRUIF8 – June 2017
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AM438x ePOS EVM Hardware
3.2
Clocks
Several clocks in the EVM support the AM438x processor. The main clock for the processor is derived
from a 25-MHz crystal. An onboard oscillator in the AM438x device generates the base clock and
subsequent module clocks as needed within the AM438x processor. A 32-kHz clock for the real-time clock
(RTC) on the AM438x device is derived from a 32.768-kHz crystal on the board.
The EVM also supports an option to connect an external clock using a subminiature version A (SMA)
connector for both these clocks. However, hardware modifications are needed to isolate the onboard
crystals and connect the external clock. See the schematics and TRM for details.
3.3
Reset Signals
Power-on reset to the processor is driven from the power good signal of the power manager and by a hard
reset switch. Asserting this switch also activates the reset signal SYS_RESETn, which runs to several
peripherals and the AM438x and resets those peripherals.
3.4
Memories Supported
3.4.1
LPDDR2 SDRAM
The AM438x ePOS EVM contains 8Gb (256M x 32, 2 dies) of LPDDR2 SDRAM memory from Micron
®
,
which has dual dies. The part number for the LPDDR2 SDRAM memory device used is
MT42L256M32D2LG-25. The package used is an 168-ball VFBGA package.
3.4.2
NAND Flash
The ePOS EVM has a NAND type of flash. The part number of the memory device used is
MT29F4G08AB, which is a 4Gb (512M × 8) of flash memory. The GPMC signals are used to
communicate with this memory.
3.4.3
QSPI Flash
A QSPI flash of 512Mb, part number MX66L51235FMI-10G, is used in this design. The QSPI flash boot is
enabled through this flash. This flash is connected to the SPI0 port of the processor.
3.4.4
Board Identity Memory
Each board contains a serial EEPROM that contains board-specific data that lets the processor
automatically detect which board is connected and the version of that board. Other hardware-specific data
can be stored on this memory device as well. The part number of the memory device is CAT24C256WI-G.
See
Section 5
for details on the data in this memory.
3.5
SDMMC0
The SDMMC0 connector on the ePOS EVM is a microSD card socket, part number MHC-W21-601. This
device is a standard SD/MMC card type of connector. The SDMMC0 connector is connected to the MMC0
port of the AM438x processor. Check the AM438x data sheet and TRM for supported card types and
densities.
3.6
10/100 Ethernet
The AM438x ePOS EVM uses the 10/100 Ethernet transceiver (DP83848J) from TI, which is connected to
the J8 RJ45 connector.
The reset on the transceiver is driven by the board system reset signal, SYS_RESETn, and the individual
reset signal, ETHER_RESETn, that is controlled by the GPIO of the AM438x processor. A 50-MHz crystal
oscillator drives the clock signal for the DP83848J device.
The PHY address is set to 0x10h.