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8.2 Register Descriptions
8.2.1 Bus Control Register (BCR)
The bus control register (BCR) is a 16-bit read/write register that selects the functions of areas and
status of bus cycles. It is initialized to H'0000 by a power-on reset, but is not initialized by a
manual reset or in standby mode.
Bit: 15 14 13 12 11 10 9 8
Bit name: DRAME IOE WARP RDDTY BAS — — —
Initial value: 0 0 0 0 0 0 0 0
R/W: R/W R/W R/W R/W R/W — — —
Bit: 7 6 5 4 3 2 1 0
Bit name: — — — — — — — —
Initial value: 0 0 0 0 0 0 0 0
R/W: — — — — — — — —
• Bit 15 (DRAM Enable Bit (DRAME)): DRAME selects whether area 1 is used as an external
memory space or DRAM space. 0 sets it as external memory space and 1 sets it as DRAM
space. The setting of the DRAM area control register is valid only when this bit is set to 1.
Bit 15: DRAME Description
0 Area 1 is external memory space (Initial value)
1 Area 1 is DRAM space
• Bit 14 (Multiplexed I/O Enable Bit (IOE)): IOE selects whether area 6 is used as external
memory space or an address/data multiplexed I/O area. 0 sets it as external memory space and
1 sets it as address/data multiplexed I/O space. With address/data multiplexed I/O space, the
address and data are multiplexed and input/output is from AD15–AD0.
Bit 14: IOE Description
0 Area 6 is external memory space (Initial value)
1 Area 6 is an address/data multiplexed I/O area
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