h8s-2158 Renesas Electronics Corporation., h8s-2158 Datasheet - Page 166

• Manufacturer Part Number: h8s-2158
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 6 Bus Controller
Wait Mode and Number of Program Wait States: When a 3-state access space is designated by
the AST bit in WSCR, the wait mode and the number of program wait states to be inserted
automatically is selected by the WMS1, WMS0, WC1, and WC0 bits in WSCR. From 0 to 3
program wait states can be selected.
When the 256-kbyte expansion area is specified as a 3-state access space by the AST256 bit in
WSCR, the wait mode and the number of program wait states to be inserted automatically is
selected by the WMS10, WC11, and WC10 bits in WSCR2. From 0 to 3 program wait states can
be selected.
When the CP/CF expansion area is specified as a 3-state access space by the ASTCP bit in BCR2,
the wait mode and the number of program wait states to be inserted automatically is selected by
the WMS21, WMS20, WC21, and WC20 bits in WSCR2. From 0 to 3 program wait states can be
selected.
When the CP expansion area is set to the CF expansion area (memory card mode) by the CFE bit
in BCR, the wait mode and the number of program wait states to be inserted automatically is
selected by the WMS21, WMS20, WC22, WC21, and WC20 bits in WSCR2. From 0 to 4, 6, 8, or
10 program wait states can be selected.
The wait function for external expansion is effective for connecting low-speed devices to the
external address space. However, this wait function may cause some problems when bus masters
other than the CPU, such as the DTC and RFU are to be delayed. The RFU is mostly used for data
transmission and reception of interface peripheral modules. In this case, the wait function for
external expansion may cause difficulty in making data transfer satisfy the communication rate of
transmit/receive data of the interface peripheral modules. To prevent such a problem, it is
recommended that when using the RFT, the external address space should be designated as a 2-
state or 3-state access space with no wait state.
Tables 6.2 to 6.7 show each bit setting and external address space division in the address ranges of
the external address space, and the bus specifications for the basic bus interface of each area.
Rev. 3.00 Jan 25, 2006 page 114 of 872
REJ09B0286-0300