7721 Datasheet, PDF (32/577 Pages) List of Unclassifed Manufacturers – H Bridge Power Module

CENTRAL PROCESSING UNIT (CPU)
2.2 Bus interface unit
2.2 Bus interface unit
A bus interface unit (BIU) is built-in between the central processing unit (CPU) and memory•I/O devices.
BIU’s function and operation are described below.
When externally connecting devices, refer to “CHAPTER 3. CONNECTION WITH EXTERNAL DEVICES.”
2.2.1 Overview
Transfer operation between the CPU and memory•I/O devices is always performed via the BIU.
ΠThe BIU reads an instruction from the memory before the CPU executes it.
 When the CPU reads data from the memory•I/O device, the CPU first specifies the address from which
data is read to the BIU. The BIU reads data from the specified address and passes it to the CPU.
Ž When the CPU writes data to the memory•I/O device, the CPU first specifies the address to which data
is written to the BIU and write data. The BIU writes the data to the specified address.
 To perform the above operations Œ to Ž, the BIU inputs and outputs the control signals, and control the
bus.
Figure 2.2.1 shows the bus and bus interface unit (BIU).
7721 Group User’s Manual
2–9