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4.6 Idle State Insertion Function
To facilitate interfacing with low-speed memory devices and meeting the data output float delay time on memory
read accesses, one idle state (TI) can be inserted into the current bus cycle after the T3 state. The bus cycle follow-
ing continuous bus cycles starts after one idle state.
Specifying insertion of the idle state is programmable by using the bus cycle control register (BCC).
Immediately after the system has been reset, idle state insertion is automatically programmed for all memory
blocks.
(1) Bus cycle control register (BCC)
This register can be read/written in 16-bit units.
After reset: AAAAH
R/W
Symbol
15
14
13
BCC
BC71
0
BC61
BCn1
1
0
Not inserted
1
Inserted
n
0
Blocks 0/1
1
Blocks 2/3
2
Blocks 4/5
3
Blocks 6/7
4
Blocks 8/9
5
Blocks 10/11
6
Blocks 12/13
7
Blocks 14/15
Block 0 is reserved for the internal ROM area; therefore, no idle state is specified regardless of the BCC setting.
The internal RAM area and on-chip peripheral I/O area of block 15 are not subject to insertion of the idle state.
Be sure to set bits 0, 2, 4, 6, 8, 10, 12, and 14 to 0. If these bits are set to 1, the operation is not guaranteed.
CHAPTER 4 BUS CONTROL FUNCTION
Address: FFFFF062H
12
11
10
9
0
BC51
0
BC41
Idle State Insert Specification
Blocks into Which Idle State Is Inserted
8
7
6
5
0
BC31
0
BC21
0
4
3
2
1
BC11
0
BC01
0
0
89
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