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CP82C59A Datasheet(PDF) 9 Page - Intersil Corporation |
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CP82C59A Datasheet(HTML) 9 Page - Intersil Corporation |
9 / 20 page 4-9 The address format is 2 bytes long (A0 - A15). When the routine interval is 4, A0 - A4 are automatically inserted by the 82C59A, while A5 - A15 are programmed externally. When the routine interval is 8, A0 - A5 are automatically inserted by the 82C59A while A6 - A15 are programmed externally. The 8-byte interval will maintain compatibility with current software, while the 4-byte interval is best for a compact jump table. In an 80C86/88/286 system, A15 - A11 are inserted in the five most significant bits of the vectoring byte and the 82C59A sets the three least significant bits according to the interrupt level. A10 - A5 are ignored and ADI (Address inter- val) has no effect. LTlM: If LTlM = 1, then the 82C59A will operate in the level interrupt mode. Edge detect logic on the interrupt inputs will be disabled. ADI: ALL address interval. ADI = 1 then interval = 4; ADI = 0 then interval = 8. SNGL: Single. Means that this is the only 82C59A in the system. If SNGL = 1, no ICW3 will be issued. IC4: If this bit is set - lCW4 has to be issued. If lCW4 is not needed, set lC4 = 0. Initialization Command Word 3 (ICW3) This word is read only when there is more than one 82C59A in the system and cascading is used, in which case SNGL = 0. It will load the 8-bit slave register. The functions of this register are: a. In the master mode (either when SP = 1, or in buffered mode when M/S = 1 in lCW4) a “1” is set for each slave in the bit corresponding to the appropriate IR line for the slave. The master then will release byte 1 of the call sequence (for 8080/85 system) and will enable the corre- sponding slave to release bytes 2 and 3 (for 80C86/88/ 286, only byte 2) through the cascade lines. b. In the slave mode (either when SP = 0, or if BUF = 1 and M/S = 0 in lCW4), bits 2 - 0 identify the slave. The slave compares its cascade input with these bits and if they are equal, bytes 2 and 3 of the call sequence (or just byte 2 for 80C86/88/286) are released by it on the Data Bus. NOTE: (The slave address must correspond to the IR line it is con- nected to in the master ID). Initialization Command Word 4 (ICW4) SFNM: If SFNM = 1, the special fully nested mode is pro- grammed. BUF: If BUF = 1, the buffered mode is programmed. In buffered mode, SP/EN becomes an enable output and the master/slave determination is by M/S. M/S: If buffered mode is selected: M/S = 1 means the 82C59A is programmed to be a master, M/S = 0 means the 82C59A is programmed to be a slave. If BUF = 0, M/S has no function. AEOI: If AEOI = 1, the automatic end of interrupt mode is programmed. µPM: Microprocessor mode: µPM = 0 sets the 82C59A for 8080/85 system operation, µPM = 1 sets the 82C59A for 80C86/88/286 system operation. Operation Command Words (OCWs) After the Initialization Command Words (lCWs) are pro- grammed into the 82C59A, the device is ready to accept interrupt requests at its input lines. However, during the 82C59A operation, a selection of algorithms can command the 82C59A to operate in various modes through the Opera- tion Command Words (OCWs). Operation Command Word 1 (OCW1) OCW1 sets and clears the mask bits in the Interrupt Mask Register (lMR) M7 - M0 represent the eight mask bits. M = 1 indicates the channel is masked (inhibited), M = 0 indicates the channel is enabled. Operation Command Word 2 (OCW2) R, SL, EOI - These three bits control the Rotate and End of Interrupt modes and combinations of the two. A chart of these combinations can be found on the Operation Com- mand Word Format. L2, L1, L0 - These bits determine the interrupt level acted upon when the SL bit is active. Operation Command Word 3 (OCW3) ESMM - Enable Special Mask Mode. When this bit is set to 1 it enables the SMM bit to set or reset the Special Mask Mode. When ESMM = 0, the SMM bit becomes a “don’t care”. SMM - Special Mask Mode. If ESMM = 1 and SMM = 1, the 82C59A will enter Special Mask Mode. If ESMM = 1 and SMM = 0, the 82C59A will revert to normal mask mode. When ESMM = 0, SMM has no effect. Fully Nested Mode This mode is entered after initialization unless another mode is programmed. The interrupt requests are ordered in priority from 0 through 7 (0 highest). When an interrupt is acknowl- edged the highest priority request is determined and its vec- tor placed on the bus. Additionally, a bit of the Interrupt Service register (IS0 - 7) is set. This bit remains set until the microprocessor issues an End of Interrupt (EOI) command OPERATION COMMAND WORDS (OCWs) A0 D7 D6 D5 D4 D3 D2 D1 D0 OCW1 1 M7M6 M5M4M3M2M1M0 OCW2 0 R SL EOI 0 0 L2 L1 L0 OCW3 0 0 ESMM SMM 0 1 P RR RIS 82C59A |
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