Bus Specifications - Renesas H8S/2368 Series Hardware Manual

6.4.2

Bus Specifications

The external space bus specifications consist of five elements: bus width, number of access states,
number of program wait states, read strobe timing, and chip select (CS) assertion period extension
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. With the DRAM interface* and burst ROM
interface, the number of access states may be determined without regard to the setting of ASTCR.
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 WTCRA and WTCRB, and
external waits by means of the WAIT pin.
Note: * The DRAM interface is not supported by the H8S/2366.
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 WTCRA and WTCRB.
From 0 to 7 program wait states can be selected. Table 6.2 shows the bus specifications (bus
width, and number of access states and program wait states) for each basic bus interface area.
Rev. 2.00, 05/03, page 134 of 820