HITACHI 3
Table 1.1
Features of the SH7020 and SH7021 Microcomputers (cont)
Feature
Description
Nine external interrupt pins (NMI,
IRQ0
–
IRQ7
)
Interrupt controller (INTC)
Thirty internal interrupt sources
Sixteen programmable priority levels
User break controller (UBC)
Generates an interrupt when the CPU or DMAC generates a bus
cycle with specified conditions
Simplifies configuration of a self-debugger
Clock pulse generator (CPG)
On-chip clock pulse generator (maximum operating frequency:
20 MHz):
20-MHz pulses can be generated from a 20-MHz crystal with a
duty cycle correcting circuit
Bus state controller (BSC)
Supports external memory access:
Sixteen-bit external data bus
Address space divided into eight areas with the following preset
features:
Bus size (8 or 16 bits)
Number of wait cycles can be defined by user.
Type of area (external memory area, DRAM area, etc.)
—
Simplifies connection to ROM, SRAM, DRAM, and
peripheral I/O
When the DRAM area is accessed:
—
RAS
and
CAS
signals for DRAM are output
—
Tp cycles can be generated to assure
RAS
precharge
time
—
Address multiplexing is supported internally, so DRAM
can be connected directly
Chip select signals (
CS0
to
CS7
) are output for each area
DRAM refresh function:
Programmable refresh interval
Supports CAS-before-RAS refresh and self-refresh modes
DRAM burst access function:
Supports high-speed access modes for DRAM
Wait cycles can be inserted by an external WAIT signal
One-stage write buffer improves the system performance
Data bus parity can be generated and checked