CHAPTER 6 BUS CONTROL FUNCTION
User’s Manual U15109EJ3V0UD
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6.2.2 Control register
(1) System control register (SYC) (V850/SC1, V850/SC2)
This register switches control signals for the bus interface.
The system control register can be read/written in 8- or 1-bit units.
After reset: 00H
R/W
Address: FFFFF064H
Symbol
7
6
5
4
3
2
1
<0>
SYC
0
0
0
0
0
0
0
BIC
BIC
Bus interface control
0
DSTB, R/W, LBEN, UBEN
Note
signals output
1
RD, WRL, WRH, UBEN
Note
signals output
Note
The UBEN signal is output regardless of the BIC bit setting in the external expansion mode (set by the
memory expansion mode register (MM)).
Caution
In the V850/SC1 and V850/SC2, when using port 9 as an I/O port, set the BIC bit to 0.
Note that the BIC bit is 0 after system reset.
6.3 Bus Access
6.3.1 Number of access clocks
The number of basic clocks necessary for accessing each resource is as follows.
Table 6-2. Number of Access Clocks
Peripheral I/O (Bus Width)
Bus Cycle Type
Internal ROM
(32 Bits)
Internal RAM
(32 Bits)
Peripheral I/O
(16 Bits)
External Memory
(16 Bits)
Instruction fetch
1
3
Disabled
3 + n
Operand data access
3
1
3
3 + n
Remarks 1.
Unit: Clock/access
2.
n:
Number of wait insertions