![](http://datasheet.mmic.net.cn/370000/-PD30101_datasheet_16680756/-PD30101_34.png)
CHAPTER 1 INTRODUCTION
3
1.4.1 Internal Structure
This section introduces each unit in the V
R
4101.
(1) Bus control unit (BCU)
In the V
R
4101, the bus control unit (BCU) transfers data between the V
R
4100 CPU core and SysAD bus.
It also controls external circuits, such as the LCD controller connected to the system bus, DRAM, ROM
(flash memory or masked ROM), and PCMCIA controller, and transfers data between the V
R
4101 and
these external devices, using the address and data buses.
(2) Real-time clock (RTC)
The real-time clock (RTC) is provided with an accurate counter that operates on a 32.768-kHz clock
pulse supplied from the clock generator. It is also provided with several counters and Compare
registers for controlling various interrupts.
(3) Deadman’s switch (DSU)
The Deadman’s switch unit (DSU) is used to check whether the processor is running normally. If the
register of this unit is not cleared by software within a specified period, the system is shut down.
(4) Interrupt control unit (ICU)
The interrupt control unit (ICU) controls interrupts that are caused by factors either internal or external
to the V
R
4101, and informs the V
R
4100 CPU core when an interrupt occurs.
(5) Power management unit (PMU)
The power management unit (PMU) outputs signals necessary to control the power of the entire system
including the V
R
4101. The signals are used to control the PLL of the V
R
4100 CPU core and the internal
clocks (PClock, TClock, and MasterOut) in low-power modes.
(6) Direct memory access address unit (DMAAU)
The direct memory access address unit (DMAAU) controls the address of five different DMA transfers.
(7) Direct memory access control unit (DCU)
The direct memory access control unit (DCU) controls the arbitration of five different DMA transfers.
(8) Clock mask unit (CMU)
The clock mask unit (CMU) controls the way the clocks TClock and MasterOut are supplied from the
V
R
4100 CPU core to internal peripheral units.
(9) General purpose I/O unit (GIU)
Basically, the general purpose I/O unit (GIU) controls 12 GPIO pins. Among the 12 GPIO pins of the
current V
R
4101 version, some pins are controlled directly by other units.
(10) Audio interface unit (AIU)
The audio interface unit (AIU) generates sound having a specified frequency, using a PWM, and outputs
sound signals. Buzzer output is also available.
(11) Keyboard interface unit (KIU)