SH7018 Datasheet, PDF (96/431 Pages) Renesas Technology Corp – SuperH™ RISC engine

7.2 Description of Registers
7.2.1 Bus Control Register 1 (BCR1)
Bit: 15
14
13
12
11
10
9
8
—
—
—
—
—
—
—
—
Initial value: 0
0
1
0
0
0
0
0
R/W: R
R
R
R
R
R
R
R
Bit: 7
6
5
4
3
2
—
—
—
— A3SZ A2SZ
Initial value: 0
0
0
0
1
1
R/W: R
R
R
R
R/W R/W
Note: Never write 1 to bits 4 to 7; doing so can result in unstable operation.
1
A1SZ
1
R/W
0
A0SZ
1
R/W
Bus control register 1 (BCR1) is a 16-bit readable/writeable register that specifies the bus size for
each CS space. Note that this chip requires that byte bus size (8 bits).
Initial settings should be written to bits 8 to 0 of BCR1 following a power-on reset, and the values
should then be left unchanged. Also, the CS spaces should not be accessed until initial setting of
the registers has been completed.
BCR1 is initialized to H'200F by a power-on reset. It is not initialized in the standby mode.
• Bits 15, 14, and 12 to 4—Reserved: These bits are always read as 0. The write value should
always be 0.
• Bit 13—Reserved: This bit is always read as 1. The write value should always be 1.
• Bit 3—CS3 Space Size Specification (A3SZ): Specifies the bus size for CS3. The SH7018
requires a byte bus size, so this bit must always be set to 0.
Bit 3: A3SZ
0
1
Description
Byte (8-bit) size
Word (16-bit) size
(Initial value)
80