INTERRUPT CONTROLLER (ICU)
5.2 ICU Related Registers
5
5.2.1 Interrupt Vector Register
Interrupt Vector Register (IVECT)
<Address: H’0080 0000>
b0
?
1
?
2
?
3
?
4
?
5
?
6
?
7
?
8
?
9
?
10
?
11
?
12
?
13
?
14
?
b15
?
IVECT
<After reset: Undefined>
b
8
Bit Name
IVECT
Function
R
R
W
N
When an interrupt request is accepted, the 16-low-order
bits of the ICU vector table address for the accepted
interrupt request source are stored in this register.
16 low-order bits of ICU vector table address
Note: • This register must always be accessed in halfwords (2 bytes). (This is a read-only register.)
The Interrupt Vector Register (IVECT) is used when an interrupt request is accepted to store the 16-low-order
bits of the ICU vector table address for the accepted interrupt request source.
Before this function can work, the ICU vector table (addresses H’0000 0094 through H’0000 0113) must have
set in it the start addresses of interrupt handlers for each internal peripheral I/O. When an interrupt request is
accepted, the 16-low-order bits of the ICU vector table address for the accepted interrupt request source are
stored in the IVECT register. In the EIT handler, read the content of this IVECT register using the LDH instruction
to get the ICU vector table address.
When the IVECT register is read, operations (1) to (4) below are automatically performed in hardware.
(1) The interrupt priority level of the accepted interrupt request source (ILEVEL) is set in the IMASK register as
a new IMASK value. (Interrupts with lower priority levels than that of the accepted interrupt request source
are masked.)
(2) The interrupt request bit for the accepted interrupt request source is cleared (not cleared for level-recognized
interrupt request sources).
(3) The interrupt request (EI) to the CPU core is deasserted.
(4) The ICU’s internal sequencer is activated to start internal processing (interrupt priority resolution).
Notes: • Do not read the Interrupt Vector Register (IVECT) in the EIT handler unless interrupts are disabled
(PSW register IE bit = "0"). In the EIT handler, furthermore, read the Interrupt Request Mask
Register (IMASK) first before reading the IVECT register.
• To reenable interrupts (by setting the IE bit to "1") after reading the Interrupt Vector Register
(IVECT), perform a dummy access to the internal memory, etc. before reenabling interrupts. (The
ICU vector table readout in the EI handler processing example in Figure 5.5.2 Typical Handler
Operation for Interrupts from Internal Peripheral I/O is an access to the internal ROM and, there-
fore, does not require adding a dummy access.)
32180 Group User’s Manual (Rev.1.0)
5-5
RENESAS [ RENESAS TECHNOLOGY CORP ]
