SH7014 Datasheet, PDF (141/754 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

8. Bus State Controller (BSC)
8.2 Description of Registers
8.2.1 Bus Control Register 1 (BCR1)
BCR1 is a 16-bit read/write register that selects multiplex I/O, and specifies the bus size of the CS
spaces.
Write bits 8 to 0 of BCR1 during the initialization stage after a power-on reset, and do not change
the values thereafter. In on-chip ROM ineffective mode, do not access any CS space other than
CS0 until after completion of register initialization.
BCR1 is initialized by power-on resets to H'200F, but is not initialized by software standbys.
Bit: 15
14
13
12
11
10
9
8
⎯
⎯
⎯
⎯
⎯
⎯
⎯
IOE
Initial value: 0
0
1
0
0
0
0
0
R/W: R
R
R
R
R
R
R
R/W
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: Do not write 1 to bits 4 to 7, as operation is not guaranteed in this case.
1
A1SZ
1
R/W
0
A0SZ
1
R/W
Bits 15, 14, 12 to 9⎯Reserved: These bits always read as 0. The write value should always be 0.
Bit 13⎯Reserved: This bit always read as 1. The write value should always be 1.
Bit 8⎯Multiplex I/O Enable (IOE): Selects the use of CS3 space as ordinary space or
address/data multiplex I/O space. A 0 selects ordinary space and a 1 selects address/data multiplex
I/O space. When address/data multiplex I/O space is selected, the address and data are multiplexed
and output from the data bus. When CS3 space is an address/data multiplex I/O space, bus size is
decided by the A14 bit (A14 = 0: 8 bit, A14 = 1: 16 bit).
Bit 8
IOE
0
1
Description
CS3 space is ordinary space
CS3 space is address/data multiplex I/O space
(initial value)
Rev.5.00 Sep. 27, 2007 Page 107 of 716
REJ09B0398-0500