HD6475328-CP10 HITACHI [Hitachi Semiconductor], HD6475328-CP10 Datasheet - Page 122

• Manufacturer Part Number: HD6475328-CP10
• Description: original Hitachi CMOS microcomputer unit (MCU)
• Manufacturer: HITACHI [Hitachi Semiconductor]

5.3 Register Descriptions
5.3.1 Interrupt Priority Registers A to D (IPRA to IPRD)
IRQ
interrupt priority registers (IPRA to IPRD). These bits specify a priority level from 7 (high) to 0
(low) for interrupts from the corresponding source. The drawing below shows the configuration
of the interrupt priority registers. Table 5-3 lists their assignments to interrupt sources.
Bit
Initial value
Read/Write
Note: Bits 7 and 3 are reserved. They cannot be modified and are always read as “0.”
Table 5-3 Assignment of Interrupt Priority Registers
Register
IPRA
IPRB
IPRC
IPRD
As table 5-3 indicates, each interrupt priority register specifies priority levels for two interrupt
sources. A user program can assign desired levels to these interrupt sources by writing “000” in
bits 6 to 4 or bits 2 to 0 to set priority level 0, for example, or “111” to set priority level 7.
A reset clears registers IPRA to IPRD to H'00, so all interrupts except NMI are initially masked.
0
, IRQ
1
, and the on-chip supporting modules are each assigned three bits in one of the four
Interrupt Request Source
Bits 6 to 4
IRQ
16-Bit FRT1
16-Bit FRT3
SCI
0
—
R
7
0
R/W
Bits 2 to 0
IRQ
16-Bit FRT2
8-Bit timer
A/D converter
6
0
1
R/W
5
0
Address
H'FFF0
H'FFF1
H'FFF2
H'FFF3
103
R/W
4
0
—
R
3
0
R/W
2
0
R/W
1
0
R/W
0
0