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Chapter 4
Bus Control Function
Preliminary User’s Manual U15839EE1V0UM00
4.5 Bus Cycle Type Control Function
In the V850E/CA2 Jupiter, the following external devices can be connected directly to each memory
block.
• SRAM, external ROM, external I/O
• Page ROM
Connected external devices are specified by the bus cycle type configuration registers 0, 1 (BCT0,
BCT1).
4.5.1 Bus cycle type configuration
(1)
Bus cycle configuration registers 0, 1(BCT0, BCT1)
These registers can be read/written in 16-bit units
Cautions: 1. Write to the BCT0 and BCT1 registers after reset, and then do not change the set
value. Also, do not access an external memory area other than that for this initial-
ization routine until initial setting of the BCT0 and BCT1 registers is finished.
However, it is possible to access external memory areas whose initialization has
been finished.
2. The bits marked as 0 are reserved. They have to leave to 0.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Initial
value
BCT0
ME3
0
0
BT30 ME2
0
0
BT20 ME1
0
0
BT10 ME0
0
0
BT00 FFFFF480H 8888H
CS3
CS2
CS1
CS0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Initial
value
BCT1
ME7
0
0
BT70 ME6
0
0
BT60 ME5
0
0
BT50 ME4
0
0
BT40 FFFFF482H 8888H
CS7
CS6
CS5
CS4
Bit Position
Bit Name
Function
15, 11, 7, 3
(BCT0)
15, 11, 7, 3
(BCT1)
MEn
(n = 0 to 7)
Memory Controller Enable
Sets memory controller operation enable for each chip select signal CSn.
12, 8, 4, 0
(BCT0),
(BCT1)
BTn0
(n = 0 to 7)
Bus Cycle Type
Specifies the device to be connected to the CSn signal...
ME
Memory Controller Operation Enable
0
Operation disable
1
Operation enable
BTn0
External Device Connected Directly to CSn signal
0
SRAM, external I/O
1
Page ROM
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