Fujitsu SK-MB9EF120-002 User Manual - Page 11

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RST_X_VDP5 also drives a LED which lights when the signal is active (low). On power-up or a press

of the reset-button, the LED will flash according to the pulse generated by the system voltage

supervisor. If the reset-button is pressed only for a short time, the pulse generated is too short to be

noticed by the eye (but it is sufficient for the hardware). Holding down the button for >~4s, generates

a permanent low-signal on reset until the button is released.

2.4 MCU Clocks

The MCU is clocked using its internal 4MHz crystal oscillator with Q1 as reference. As this is the main

clock reference, it controls all timing of the microcontroller when selected.

Q2 is a 32.768kHz crystal connected to the microcontroller's real-time clock oscillator. This clock is

used to track time, while the other crystal oscillator is disabled.

The board provides two interfaces for external communication and two flash-devices for data-storage.

Two port-signals (P0_45, P0_47) are connected to a USB-Serial converter chip (FT232R from FTDI).

The ports can be controlled by USART0, thus allowing a serial interface between the MCU and a PC.

For the FT232R, drivers exist for all major operating systems (OSX, Linux, Windows) wither built-in

(Linux) or for download (Windows). They provide a standard serial interface ("COM-port"/"ttyUSB") to

the applications, so any terminal program can be used to transmit data between the MCU and a PC.

The interface does not provide hardware-handshake, thus it is left to the software to provide some

kind of flow-control and/or resynchronization, if necessary.

There is one LED per direction (RX, TX) signalling data-transmission.

The two ports can be disconnected from the converter by two jumpers, freeing them for other usage

(the two signals are also available on the B2B connector CN1).

The FT232R is powered from the USB-connector, making its operation independent on the power-

status of the board. However, as the supply of the serial interface I/O lines is powered from VDP5, the

voltages here always match the requirements of the connected port-signals.

Two ports from the MCU (P0_20, P0_21) are connected to a CAN-Bus transceiver. The CAN-bus

itself is connected to a standard D-sub connector. The two signals are also RX and TX of the internal

CAN0-controller.

As with the UART, jumpers are available for each port to disconnect them from the interface, freeing

them for use from the B2B connector CN1.

There are two serial flash devices Spansion S25FL129P. One is connected to the MCU's HSSPI-port.

It provides data-storage for applications. The second flash is of the same type, but connects to the

GFXSPI-port which can be accessed by the graphics-controller without CPU intervention. The actual

device chosen supports Quad-SPI mode at up to 80MHz, resulting in a max. data rate of 40MB/s.

SK-MB9EF120-002,-003

Hardware

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UG-9E0010-11