Energy micro EFM32 Giant Gecko Starter Kit, User Manual

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...the world's most energy friendly microcontrollers
2012-05-31 - t0014_0.11 9
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Figure 5.6. NAND Flash Interface
PD15 NAND_R/B#
PD14 NAND_CE#
PD13 NAND_WP#
PF9 EBI_RE#
PF8 EBI_WE#
PC2 EBI_A25
PC1 EBI_A24
PE[ 15..8] EBI_AD[ 7..0]
PB15 NAND_PWR_EN
I/O[ 7..0]
R/B#
ALE
CLE
WE#
RE#
CE#
WP#
VMCU
EFM32 MCU
NAND256W3A
A separate power switch is used to enable/disable the NAND flash, thus avoiding excess current draw
when not used. When NAND_PWR_EN is high, the NAND flash is powered from the same supply as
the EFM32 MCU. It is recommended to keep the write-protect line low during power transitions.
The ALE (address latch enable) and CLE (command latch enable) pins of the NAND Flash are connected
to the EBI Address pins 24 and 25, and the CE (chip enable) line is connected to a general GPIO pin.
This causes the NAND data, address and command registers to be mapped in the EFM32's address
space as:
Data register: 0x80000000
Address register: 0x81000000
Command register: 0x82000000
5.7 Backup Domain Capacitor
A small super capacitor is provided to evaluate the EFM32 Giant Gecko MCU's backup power domain.
The capacitor has a nominal value of 33 mF, and is connected with a 100 ohm series resistor to the
BU_VIN pin of the EFM32.
Because of the extremely low power consumption of the EFM32 in backup mode (400nA), the capacitor
can power a clock application using the low frequency crystal oscillator (LFXO) for more than 8 hours.
The series resistor allows measuring of the current drawn from the capacitor into the EFM32 device, by
simply using a multimeter to measure the voltage across it. Please refer to the schematic and assembly
drawings to locate the series resistor.
5.8 USB Micro-AB Connector
The EFM32GG-STK3700 board is equipped with a USB Micro-AB connector supporting USB Device
and Embedded Host modes. The figure below shows how the USB lines are connected to the EFM32.
The USB_VBUSEN line is connected to a current limited switch which supplies the VBUS line with 5V
when operating as a USB Host. The current limited switch also has a flag signal connected to the EFM32
which can notify it in case excessive current is drawn by the attached device. Note that the "J-Link" USB
cable must be inserted to provide 5V to the device when operating the EFM32 in host mode.