p2125vps20 Renesas Electronics Corporation., p2125vps20 Datasheet - Page 158

• Manufacturer Part Number: p2125vps20
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 6 Bus Controller (BSC)
6.6
In this LSI, the external address space can be designated as the burst ROM space by setting the
BRSTRM bit in BCR to 1, and the burst ROM interface enabled. Consecutive burst accesses of a
maximum four or eight words can be performed only during CPU instruction fetch. 1 or 2 states
can be selected for burst ROM access.
6.6.1
The number of access states in the initial cycle (full access) of the burst ROM interface is
determined by the AST bit in WSCR. When the AST bit is set to 1, wait states can be inserted. 1
or 2 states can be selected for burst access according to the setting of the BRSTS1 bit in BCR.
Wait states cannot be inserted in a burst cycle. Burst accesses of a maximum four words is
performed when the BRSTS0 bit in BCR is cleared to 0, and burst accesses of a maximum eight
words is performed when the BRSTS0 bit in BCR is set to 1.
The basic access timing for the burst ROM space is shown in figures 6.8 and 6.9.
Rev. 1.00 Sep. 21, 2006 Page 120 of 658
REJ09B0310-0100
Figure 6.8 Access Timing Example in Burst ROM Space (AST = BRSTS1 = 1)
Burst ROM Interface
Basic Operation Timing
Address bus
(IOSE = 0)
Data bus
AS/IOS
RD
φ
T
1
Full access
T
2
Read data
T
3
T
1
Only lower address changes
Read data
T
Burst access
2
T
1
Read data
T
2