h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 197

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

Bits 1 and 0—Wait Count 1 and 0 (WC1, WC0): These bits select the number of program wait
states when external memory space is accessed while the AST bit is set to 1.
6.3
6.3.1
The external space bus specifications consist of three elements: bus width, number of access
states, and wait mode and number of program wait states.
The bus width and number of access states for on-chip memory and internal I/O registers are
fixed, and are not affected by the bus controller.
Bus Width: A bus width of 8 or 16 bits can be selected with the ABW bit. A 16-bit access space
cannot be specified for these group.
Number of Access States: Two or three access states can be selected with the AST bit.
When 2-state access space is designated, wait insertion is disabled. The number of access states on
the burst ROM interface is determined without regard to the AST bit setting.
Wait Mode and Number of Program Wait States: When 3-state access space is designated by
the AST bit, the wait mode and the number of program wait states to be inserted automatically is
selected with WMS1, WMS0, WC1, and WC0. From 0 to 3 program wait states can be selected.
Table 6.3 shows the bus specifications for each basic bus interface area.
Bit 1
WC1
0
1
Overview of Bus Control
Bus Specifications
Bit 0
WC0
0
1
0
1
Description
No program wait states are inserted
1 program wait state is inserted in external memory space accesses
2 program wait states are inserted in external memory space accesses
3 program wait states are inserted in external memory space accesses
Rev. 4.00 Jun 06, 2006 page 143 of 1004
Section 6 Bus Controller
REJ09B0301-0400
(Initial value)