
CHAPTER 1 INTRODUCTION
User’s Manual U14272EJ3V0UM
31
1.3.1 CPU core
The V
R
4181 integrates an NEC Electronics’ V
R
4110 CPU core supporting both the MIPS III and MIPS16
instruction sets.
The V
R
4181 supports the following pipeline clock (PClock) and internal bus clock (TClock) frequencies. The
PClock is set by attaching pull-up or pull-down resistors to the CLKSEL(2:0) pins. The frequency of the TClock, which
is used in MBA bus, is set by PMUDIVREG register in Power Management Unit.
Table 1-1. Supported PClock and TClock Frequencies
PClock frequency
TClock frequency
65.4 MHz
65.4/32.7/21.8 MHz
62.0 MHz
62.0/31.0/20.7 MHz
49.1 MHz
49.1/24.6 MHz
The V
R
4110 core of the V
R
4181 includes 4 KB of instruction cache and 4 KB of data cache.
The V
R
4110 core also supports the following power management modes:
Fullspeed
Standby
Suspend
Hibernate
Note
Note
Suspend mode is supported only when the internal LCD controller has been disabled or the LCD panel
has been powered off.
1.3.2 Bus interface
The V
R
4181 incorporates single bus architecture. All external memory and I/O devices are connected to the same
22-bit address bus and 16-bit data bus. These external address and data bus are together called the system bus.
When the external bus operates at a very high speed, the DRAM data bus must be isolated from other low speed
devices such as ROM array. The V
R
4181 provides two pins, SYSEN# and SYSDIR, to control the data buffers for this
isolation.
The V
R
4181 supports the following types of devices connected to the system bus.
Table 1-2. Devices Supported by System Bus
Device
Data width
ROM, flash memory
16 bits only
DRAM
16 bits only
CompactFlash
8 or 16 bits
External I/O
8 or 16 bits
External memory
8 or 16 bits
Six of the external bus interface signals, IORD#, IOWR#, IORDY, IOCS16#, MEMCS16# and RESET#, can be
individually defined as general-purpose I/O pins or LCD interface pin if they are not needed by external system
components.