
Rev. 2.0, 09/02, page 130 of 732
9.5
Description of Registers
9.5.1
Bus Control Register 1 (BCR1)
BCR1 is a 16-bit readable/writable register that enables access to the MTU control registers and
specifies the bus size of each CS space. When using the SH7144, specify the bus size as word (16-
bit) or smaller size.
Write bits 7 to 0 of BCR1 during the initialization stage after a power-on reset, and do not change
the values thereafter. In on-chip ROM enabled mode, do not access any of each CS space until
completion of register initialization. In on-chip ROM disabled mode, do not access CS spaces
other than CS0 until completion of register initialization.
Bit
Bit Name Initial Value
R/W
Description
15
0
R
Reserved
This bit is always read as 0 and should always be
written with 0.
14
1
R
Reserved
This bit is always read as 1 and should always be
written with 1.
13
MTURWE 1
R/W
MTU Read/Write Enable
This bit enables MTU control register access. For
details, refer to section 11, Multi-Function Timer
Pulse Unit (MTU).
0: MTU control register access is disabled
1: MTU control register access is enabled
12 to 8
All 0
R
Reserved
These bits are always read as 0 and should always
be written with 0.
7
A3LG
0
R/W
CS3 space longword
This bit specifies the CS3 space bus size. This bit is
valid only for the SH7145.
This bit is reserved in SH7144. This bit is always read
as 0 and should always be written with 0.
0: Depends on the value set with the A3SZ bit in this
register.
1: Longword (32 bits)