S3C80M4/F80M4
INTERRUPT STRUCTURE
5-9
SYSTEM MODE REGISTER (SYM)
The system mode register, SYM (set 1, DEH), is used to globally enable and disable interrupt processing and to
control fast interrupt processing (see Figure 5-5).
A reset clears SYM.1, and SYM.0 to "0". The 3-bit value for fast interrupt level selection, SYM.4–SYM.2, is
undetermined.
The instructions EI and DI enable and disable global interrupt processing, respectively, by modifying the bit 0
value of the SYM register. In order to enable interrupt processing an Enable Interrupt (EI) instruction must be
included in the initialization routine, which follows a reset operation. Although you can manipulate SYM.0 directly
to enable and disable interrupts during the normal operation, it is recommended to use the EI and DI instructions
for this purpose.
System Mode Register (SYM)
DEH, Set 1, R/W
.7
.6
.5
.4
.3
.2
.1
.0
MSB
LSB
Global interrupt enable bit:
(3)
0 = Disable all interrupts processing
1 = Enable all interrupts processing
Fast interrupt enable bit:
(2)
0 = Disable fast interrupts processing
1 = Enable fast interrupts processing
Fast interrupt level
selection bits:
(1)
0 0 0 = IRQ0
0 0 1 = IRQ1
0 1 0 = IRQ2
0 1 1 = IRQ3
1 0 0 = IRQ4
1 0 1 = IRQ5
1 1 0 = IRQ6
1 1 1 = IRQ7
Not used for the S3C80M4
Always logic "0"
NOTES:
1. You can select only one interrupt level at a time for fast interrupt processing.
2. Setting SYM.1 to "1" enables fast interrupt processing for the interrupt processing for the
interrupt level currently selected by SYM.2-SYM.4.
3. Following a reset, you must enable global interrupt processing by executing EI instruction
(not by writing a "1" to SYM.0)
Figure 5-5. System Mode Register (SYM)
Summary of Contents for S3C80M4/F80M4
Page 1: ...S3C80M4 F80M4 8 BIT CMOS MICROCONTROLLERS USER S MANUAL Revision 1 ...
Page 44: ...ADDRESS SPACES S3C80M4 F80M4 2 20 NOTES ...
Page 84: ...CONTROL REGISTERS S3C80M4 F80M4 4 26 NOTES ...
Page 102: ...INTERRUPT STRUCTURE S3C80M4 F80M4 5 18 NOTES ...
Page 190: ...INSTRUCTION SET S3C80M4 F80M4 6 88 NOTES ...
Page 202: ...RESET and POWER DOWN S3C80M4 F80M4 8 6 NOTES ...
Page 216: ...8 BIT TIMER 0 S3C80M4 F80M4 11 4 NOTES ...
Page 220: ...8 BIT PULSE WIDTH MODULATION S3C80M4 F80M4 12 4 NOTES ...
Page 230: ...ELECTRICAL DATA S3C80M4 F80M4 13 10 NOTES ...