h8s-2649 Renesas Electronics Corporation., h8s-2649 Datasheet - Page 151

• Manufacturer Part Number: h8s-2649
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

Section 7 Bus Controller (BSC)
7.4.2
Bus Specifications
The external address space bus specifications consist of three elements: bus width, number of
access states, 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 ABWCR. An area for which an 8-bit
bus is selected functions as an 8-bit access space, and an area for which a 16-bit bus is selected
functions as a 16-bit access space. If all areas are designated as 8-bit access space, 8-bit bus mode
is set; if any area is designated as 16-bit access space, 16-bit bus mode is set.
Number of Access States: Two or three access states can be selected with ASTCR. An area for
which 2-state access is selected functions as a 2-state access space, and an area for which 3-state
access is selected functions as a 3-state access space.
When 2-state access space is designated, wait insertion is disabled. When 3-state access space is
designated, it is possible to insert program waits by means of the WCRH and WCRL, and external
waits by means of the WAIT pin.
Number of Program Wait States: When 3-state access space is designated by ASTCR, the
number of program wait states to be inserted automatically is selected with WCRH and WCRL.
From 0 to 3 program wait states can be selected.
Table 7.2 shows the bus specifications (bus width, number of access states, and program wait
states) for each basic bus interface area.
Rev. 2.00 Dec. 05, 2005 Page 113 of 724
REJ09B0200-0200