h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 207

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

6.5
6.5.1
With the H8S/2138 Group and H8S/2134 Group, external space area 0 can be designated as burst
ROM space, and burst ROM interfacing can be performed.
External space can be designated as burst ROM space by means of the BRSTRM bit in BCR.
Consecutive burst accesses of a maximum of 4 words or 8 words can be performed for CPU
instruction fetches only. One or two states can be selected for burst access.
6.5.2
The number of states in the initial cycle (full access) of the burst ROM interface is in accordance
with the setting of the AST bit. Also, when the AST bit is set to 1, wait state insertion is possible.
One or two states can be selected for the burst cycle, according to the setting of the BRSTS1 bit in
BCR. Wait states cannot be inserted.
When the BRSTS0 bit in BCR is cleared to 0, burst access of up to 4 words is performed; when
the BRSTS0 bit is set to 1, burst access of up to 8 words is performed.
The basic access timing for burst ROM space is shown in figures 6.8 (a) and (b). The timing
shown in figure 6.8 (a) is for the case where the AST and BRSTS1 bits are both set to 1, and that
in figure 6.8 (b) is for the case where both these bits are cleared to 0.
Burst ROM Interface
Overview
Basic Timing
Rev. 4.00 Jun 06, 2006 page 153 of 1004
Section 6 Bus Controller
REJ09B0301-0400