Bus Cycle Type Control Function; Bus Cycle Type Configuration Register (Bct) - NEC V850E/MS1 UPD703100 User Manual

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 14 13
BCT BT71 BT70 BT61 BT60
Memory
7 6
block
Bit Position Bit Name
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.
CHAPTER 4 BUS CONTROL FUNCTION
12 11 10 9 8 7
BT51 BT50 BT41 BT40 BT31
5 4 3
Bus Cycle Type
Specifies the external device connected to memory block n.
BTn1 BTn0
0 0
0 1
1 0
1 1
User's Manual U12688EJ4V0UM00
6 5 4 3 2 1
BT30 BT21 BT20 BT11 BT10 BT01
2 1
Function
External Device Connected Directly to Memory Block n
SRAM, external ROM, external I/O
Page ROM
Note
DRAM
Setting prohibited
0
Address After reset
BT00
FFFFF064H
0
0000H
105