CHAPTER 4 BUS CONTROL FUNCTION
User’s Manual U12688EJ4V0UM00
105
4.4
Bus Cycle Type Control Function
In the V850E/MS1, the following external devices can be connected directly to each memory block.
• SRAM, external ROM, external I/O
• Page ROM
• DRAM
Connected external devices are specified by the bus cycle type configuration register (BCT).
4.4.1 Bus cycle type configuration register (BCT)
This register can be read /written in 16-bit units.
15
BT71
BCT
Memory
block
Address
FFFFF064H
After reset
0000H
14
BT70
13
BT61
12
BT60
11
BT51
10
BT50
9
BT41
8
BT40
7
BT31
6
BT30
5
BT21
4
BT20
3
BT11
2
BT10
1
BT01
0
BT00
7
6
5
4
3
2
1
0
Bit Position
Bit Name
Function
Bus Cycle Type
Specifies the external device connected to memory block n.
BTn1
BTn0
External Device Connected Directly to Memory Block n
0
0
SRAM, external ROM, external I/O
0
1
Page ROM
1
0
DRAM
Note
1
1
Setting prohibited
15 to 0
BTn1,
BTn0
(n = 7 to 0)
Note Using the DTC register, one DRAM access type setting can be selected out of 4 types for each memory
block (refer to 5.3.5 DRAM type configuration register (DTC)).
Caution Write to the BCT register after reset, and then do not change the set value. Also, do not access
an external memory area other than the one for this initialization routine until the initial setting
of the BCT register is complete. However, it is possible to access an external memory area
whose initialization is complete.
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