
Semiconductor Group
125
Interrupt System
8.4
External Interrupts
The external interrupts 0 and 1 can be programmed to be level-activated or negative-transition
activated by setting or clearing bit IT0 or IT1, respectively, in register TCON (see figure 8-4).
lf ITx = 0 (x = 0 or 1), external interrupt x is triggered by a detected low level at the INTx pin.
lf ITx = 1, external interrupt x is negative edge-triggered. In this mode, if successive samples of the
INTx pin show a high in one cycle and a low in the next cycle, interrupt request flag lEx in TCON is
set. Flag bit lEx then requests the interrupt.
lf the external interrupt 0 or 1 is level-activated, the external source has to hold the request active
until the requested interrupt is actually generated. Then it has to deactivate the request before the
interrupt service routine is completed, or else another interrupt will be generated.
The external interrupts 2 and 3 can be programmed to be negative or positive transition-activated
by setting or clearing bit I2FR or I3FR in register T2CON (see figure 8-5). lf IxFR = 0 (x = 2 or 3),
external interrupt x is negative transition-activated. lf IxFR = 1, external interrupt is triggered by a
positive transition.
The external interrupts 4, 5, and 6 are activated by a positive transition. The external timer 2 reload
trigger interrupt request flag EXF2 will be activated by a negative transition at pin P1.5/T2EX but
only if bit EXEN2 is set.
Since the external interrupt pins (INT2 to INT6) are sampled once in each machine cycle, an input
high or low should be held for at least 12 oscillator periods to ensure sampling. lf the external
interrupt is transition-activated, the external source has to hold the request pin low (high for INT2
and INT3, if it is programmed to be negative transition-active) for at least one cycle, and then hold
it high (low) for at least one cycle to ensure that the transition is recognized so that the
corresponding interrupt request flag will be set (see figure 8-10). The external interrupt request
flags will automatically be cleared by the CPU when the service routine is called.
*
Содержание SAB 80515 Series
Страница 9: ...Semiconductor Group 9 Introduction Figure 1 2 Block Diagram ...
Страница 12: ...Semiconductor Group 12 Fundamental Structure Figure 2 1 Detailed Block Diagram ...
Страница 18: ...Semiconductor Group 18 Central Processing Unit Figure 3 1 Fetch Execute Sequence ...
Страница 22: ...Semiconductor Group 22 Memory Organization Figure 4 3 Mapping of the Lower Portion of the Internal Data Memory ...
Страница 30: ...Semiconductor Group 30 External Bus Interface Figure 5 1 a and b External Program Memory Execution ...
Страница 38: ...Semiconductor Group 38 On Chip Peripheral Components Figure 7 3 Output Driver Circuits of Ports 1 through 5 ...
Страница 59: ...Semiconductor Group 59 On Chip Peripheral Components Figure 7 16 a Functional Diagram Serial Interface Mode 0 ...
Страница 60: ...Semiconductor Group 60 On Chip Peripheral Components Figure 7 16 b Timing Diagram Serial Interface Mode 0 ...
Страница 61: ...Semiconductor Group 61 On Chip Peripheral Components Figure 7 17 a Functional Diagram Serial Interface Mode 1 ...
Страница 62: ...Semiconductor Group 62 On Chip Peripheral Components Figure 7 17 b Timing Diagram Serial Interface Mode 1 ...
Страница 73: ...Semiconductor Group 73 On Chip Peripheral Components Figure 7 25 A D Converter Block Diagram ...
Страница 83: ...Semiconductor Group 83 On Chip Peripheral Components Figure 7 33 a Timer 2 Block Diagram ...
Страница 111: ...Semiconductor Group 111 On Chip Peripheral Components Figure 7 54 Timing Diagram System Clock Output ...
Страница 113: ...Semiconductor Group 113 Interrupt System Figure 8 1 a Interrupt Structure of the SAB 80 C 515 80 C 535 ...
Страница 114: ...Semiconductor Group 114 Interrupt System Figure 8 1 b Interrupt Structure of the SAB 80 C 515 80 C 535 cont d ...
Страница 204: ...Semiconductor Group 204 Instruction Set XCH A Ri Operation XCH A Ri Bytes 1 Cycles 1 Encoding 1 1 0 0 0 1 1 i ...
Страница 215: ...Device Specifications Semiconductor Group 215 ...
Страница 217: ...Device Specifications Semiconductor Group 217 Pin Configuration P LCC 68 ...
Страница 219: ...Device Specifications Semiconductor Group 219 Logic Symbol ...
Страница 226: ...Device Specifications Semiconductor Group 226 Figure 1 Block Diagram ...
Страница 229: ...Device Specifications Semiconductor Group 229 Figure 2 Memory Address Spaces ...
Страница 239: ...Device Specifications Semiconductor Group 239 Figure 4 Block Diagram of the A D Converter ...
Страница 241: ...Device Specifications Semiconductor Group 241 Figure 5 Interrupt Request Sources ...
Страница 242: ...Device Specifications Semiconductor Group 242 Figure 6 Interrupt Priority Level Structure ...
Страница 268: ...Device Specifications Semiconductor Group 268 AC Testing Input Output Waveforms AC Testing Float Waveforms ...