HD6412240 RENESAS [Renesas Technology Corp], HD6412240 Datasheet - Page 188

• Manufacturer Part Number: HD6412240
• Description: Renesas 16-Bit Single-Chip Microcomputer H8S Family / H8S/2200 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 6 Bus Controller
6.3.2
Bus Specifications
The external space bus specifications consist of three elements: (1) bus width, (2) number of
access states, and (3) 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.
(1) 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 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.
(2) 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 states is one or two regardless of the ASTCR setting.
When 2-state access space is designated, wait insertion is disabled.
(3) 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.
Rev.3.00 Mar. 26, 2007 Page 146 of 772
REJ09B0355-0300