Bus Control Register 2 (Bcr2) - Hitachi SH7751 Hardware Manual

13.2.2

Bus Control Register 2 (BCR2)

Bus control register 2 (BCR2) is a 32-bit readable/writable register that specifies the bus width for
each area, and whether a 16-bit port is used.
BCR2 is initialized to H'3FFC by a power-on reset, but is not initialized by a manual reset or in
standby mode. External memory space other than area 0 should not be accessed until register
initialization is completed.
Bit: 15
A0SZ1
Initial value: 0/1*
R/W: R
Bit: 7
A3SZ1
Initial value: 1
R/W: R/W
Note: * These bits sample the values of the external pins that specify the area 0 bus size.
Bits 15 and 14—Area 0 Bus Width (A0SZ1, A0SZ0): These bits sample the external pins (MD3
and MD4) that specify the bus size in a power-on reset. They are read-only bits.
Bit 15: MD4
0
1
Rev. 3.0, 04/02, page 326 of 1064
14 13
A0SZ0 A6SZ1
0/1* 1
R R/W
6 5
A3SZ0 A2SZ1
1 1
R/W R/W
Bit 14: MD3
0
1
0
1
12 11
A6SZ0 A5SZ1
1 1
R/W R/W
4 3
A2SZ0 A1SZ1
1 1
R/W R/W
Bus Width
Reserved (Setting prohibited)
8 bits
16 bits
32 bits
10 9
A5SZ0 A4SZ1
1 1
R/W R/W
2 1
A0SZ0 — PORTEN
1 0
R/W —
8
A4SZ0
1
R/W
0
0
R/W