HD64F2636F20 Datasheet, PDF (214/1512 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2600 Series

Section 7 Bus Controller
H8S/2639, H8S/2638, H8S/2636,
H8S/2630, H8S/2635 Group
7.3.2 Bus Specifications
The external 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 ADWCR. 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 a16-bit access space.
If all areas are designated for 8-bit access, 8-bit bus mode is set; if any area is designated for 16-bit
access, 16-bit bus mode is set. When the burst ROM interface is designated, 16-bit bus mode is
always 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.
With the burst ROM interface, the number of access states may be determined without regard to
ASTCR.
When 2-state access space is designated, wait insertion is disabled.
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 7-3 shows the bus specifications for each basic bus interface area.
Page 164 of 1458
REJ09B0103-0800 Rev. 8.00
May 28, 2010