m37905 Renesas Electronics Corporation., m37905 Datasheet - Page 33

• Manufacturer Part Number: m37905
• Description: Mitsubishi 16-bit Single-chip Microcomputer 7700 Family / 7900 Series
• Manufacturer: Renesas Electronics Corporation.

registers.
and SFR).
CENTRAL PROCESSING UNIT (CPU)
2.2 Bus interface unit (BIU)
2.2 Bus interface unit (BIU)
The bus interface unit (hereafter called “BIU”) performs the following two operations:
Figure 2.2.1 shows the bus and BIU.
BIU is structured with four kinds of registers shown in Figure 2.2.2. Table 2.2.1 lists the function of the BIU
Fig. 2.2.1 Bus and BIU
Fig. 2.2.2 BIU registers’ structure
In the M37905, the internal buses are used when the CPU accesses the internal area (the internal memory
2-10
b31
Instruction prefetch
Data transfer (read and write)
b23
b23
M37905
SFR : Special Function Register
processing
The CPU bus and internal bus are independent of one another.
DQ
Central
(CPU)
unit
PA
DA
b7
Q
Q
0
9
b0
b0
b0
b0
CPU bus
Program address register
Instruction queue buffer
Data address register
Data buffer
interface
(BIU)
Bus
unit
7905 Group User’s Manual Rev.1.0
Internal address bus (AD
Internal control signal
Internal code bus (CB
Internal data bus (DB
Table 2.2.1 Functions of BIU registers
Program
address
register
Instruction
queue buffer
Data address
register
Data buffer
Name
Internal buses
0
0
0
to AD
Indicates a storage address of the
instruction to be fetched into an
instruction queue buffer, next.
Temporarily stores an instruction
which has been fetched.
Indicates an address from which data
will be read or to which data will be
written, next.
Temporarily stores data which has
been read from memory•I/O device
by BIU or which will be written to
memory•I/O device by the CPU.
to DB
to CB
23
15
31
)
)
)
Functions
peripheral
memory
Internal
Internal
devices
(SFR)