APPENDIX A DIFFERENCES BETWEEN V
R
4102 AND V
R
4101
687
A.2.3 BCU
(1) Setting of BCU Transaction
In the V
R
4101, the intervals of bus transactions and the number of repetitions in the enabled BCU transaction
intervals can be selectable. This function is deleted in the V
R
4102.
(2) Memory Access Control
16 and 32 bits are selectable as the data bus width with DBUS32 pin at reset in the V
R
4102 except for ISA
memory area, on the other hand, the bus width is fixed to 16 bits in the V
R
4101.
Though both the V
R
4102 and the V
R
4101 can select three memory types which are DRAM, masked ROM, and
Flash memory, their memory sizes and mapping method are different as summarized below.
Memory type
V
R
4102
V
R
4101
DRAM
Masked ROM
16M-bit/64M-bit EDO x 16 bits (access time: 60 ns)
32M-bit/64M-bit ordinary or page type x 16 bits
16-bit bus mode: selected as banks0/1 or 2/3
32-bit bus mode: selected as bank0 or 1
16-bit bus mode: selected as banks0/1 or 2/3
32-bit bus mode: selected as bank0 or 1
16M-bit EDO x 16 bits (access time: 60 ns)
32M-bit ordinary or page type x 16 bits
The whole ROM space is selected
Flash memory
To use the whole ROM space can be selected
(3) LCD Space
The LCD space is used only for LCD access in the V
R
4101, while it can be used for either LCD access or high-
speed memory access in the V
R
4102. Which of LCD or high-speed memory the LCD space is used for is
selected in BCUCNT1REG register. When high-speed memory is selected, LCDCS# pin becomes active.
The access time for LCD is selectable among 2, 4, 6, and 8 TClock cycles in both the V
R
4102 and the V
R
4101.
For high-speed memory in the V
R
4102, the access time is selectable among 1, 2, 3, 4, 5, 6, 7, and 8 TClock
cycles. These selections of access time are set in BCUSPEEDREG register.
When transferring LCD data, inverting the data values or not is selectable in the V
R
4102 and is set in
BCUCNT2REG register. On the other hand, the V
R
4101 always inverts the values at LCD data transfer.
(4) ISA Space
In the V
R
4102, the bus size is dynamically controlled at every bus cycle with IOCS# and MEMCS# pins. In the
V
R
4101, the bus size is fixed to 8 or 16 bits and is distinguished by the accessed address space.
(5) Others
The V
R
4102 has bus hold function and can make ISA, LCD, and memory interfaces into bus hold state. The
V
R
4101 has no bus hold function, and therefore the CPU is always master state.
Bit 11..8 and bit 3..0 of PREVIDREG register indicate the revision number of the on-chip peripheral units in both
the V
R
4102 and the V
R
4101. In addition, bit 15..12 indicates the processor revision number in the V
R
4102,
though it is fixed to 0 in the V
R
4101. The remaining bits, bit 7..4, are fixed to 0 in both processors.