h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 196

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 6 Bus Controller
Bit 7—RAM Select (RAMS)/Bit 6—RAM Area Setting (RAM0): These are reserved bits.
Always write 0 when writing to these bits in the A-mask version.
Bit 5—Bus Width Control (ABW): Specifies whether the external memory space is 8-bit access
space or 16-bit access space.
However, a 16-bit access space cannot be specified for these group, and therefore 0 should not be
written to this bit.
Bit 5
ABW
0
1
Bit 4—Access State Control (AST): Specifies whether the external memory space is 2-state
access space or 3-state access space, and simultaneously enables or disables wait state insertion.
Bit 4
AST
0
1
Bits 3 and 2—Wait Mode Select 1 and 0 (WMS1, WMS0): These bits select the wait mode
when external memory space is accessed while the AST bit is set to 1.
Bit 3
WMS1
0
1
Rev. 4.00 Jun 06, 2006 page 142 of 1004
REJ09B0301-0400
Description
External memory space is designated as 16-bit access space (A 16-bit access space
cannot be specified for these group)
External memory space is designated as 8-bit access space
Description
External memory space is designated as 2-state access space
Wait state insertion in external memory space accesses is disabled
External memory space is designated as 3-state access space
Wait state insertion in external memory space accesses is enabled
Bit 2
WMS0
0
1
0
1
Description
Program wait mode
Wait-disabled mode
Pin wait mode
Pin auto-wait mode
(Initial value)
(Initial value)
(Initial value)