SH7014 datasheet(141/754 Pages) RENESAS

141 / 754 page

8. Bus State Controller (BSC)

Rev.5.00 Sep. 27, 2007 Page 107 of 716

REJ09B0398-0500

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:

⎯

IOE

Initial value:

R/W:

R/W

Bit:

⎯

A3SZ

A2SZ

A1SZ

A0SZ

Initial value:

R/W:

R/W

Note:

Do not write 1 to bits 4 to 7, as operation is not guaranteed in this case.

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

Description

CS3 space is ordinary space

(initial value)

CS3 space is address/data multiplex I/O space

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