IA88C00
Data Sheet
Microcontroller
As of Production Version -01
When an interrupt in one of the 8 levels occurs and the corresponding mask bit is not set, the level bit of
the interrupt is set to 1. The interrupt structure contains 8 levels of interrupt, 16 vectors and 27 sources.
Interrupt priority is assigned by level and controlled by the Interrupt Priority Register (IPR)
ControlRegR255B0. Each level is masked (or enabled) according to the bits in the Interrupt Mask
Register (IMR) SystemRegR221. Each bit of the Interrupt Mask register corresponds to one of the 8
levels of interrupts, IRQ register (SystemRegR220). When the corresponding bit in the Interrupt Mask
register is set to one, that level interrupt is disabled.
Figure 18. System Mode Register (SYM), R222
Bit
7
Not
Used
?
6
Not
Used
?
5
Not
Used
?
4
3
2
1
0
FIS2
FSI1
FSI0
FSE
GIE
Initial Value
Read/Write
?
R/W
?
R/W
?
R/W
?
R/W
?
R/W
R/W
R/W
R/W
The Fast Interrupt Select (FSI) selects which level interrupt can be treated as a fast interrupt. Fast
Interrupt Enable (FSE), when set to 1, enables the selected level for fast interrupt. Global Interrupt Enable
(GIE), when set to 1, enables interrupts in general.
Figure 19. Halt Mode Register (HMR), R223
Bit
7
Not
Used
?
6
Not
Used
?
5
Not
Used
?
4
Not
Used
?
3
2
1
0
D3
D2
D1
D0
Initial Value
Read/Write
1
R/W
1
R/W
1
R/W
1
R/W
R/W
R/W
R/W
R/W
D3 - CPU HALT mode - Writing a zero to this bit will invoke the HALT mode upon the execution of the
WFI instruction. The UART and counters can be halted only if D3 is 0. During HALT the internal CPU
clock is disabled, and no address strobe is generated. A hardware reset sets this bit to a 1.
D2 - Disable UART - Writing a zero to the bit will disable the UART. No interrupt request will be
generated. A 1 will make the UART and its interrupt logic remain active in HALT mode. A hardware
reset forces this bit to a 1.
D1 - Disable CT1 - Similar to CT0. When the counters are cascaded, the HALT mode 32-bit counter is
determined by the logical state of D1. A hardware reset forces this bit to a 1.
D0 - Disable CT0 - Writing a zero to this bit will disable the CT0 in HALT mode. No interrupt request
will be generated in this case. A 1 will keep the CT0 active. A hardware reset forces this bit to a 1.
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