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ST78C34IP40 数据表(PDF) 7 Page - Exar Corporation |
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ST78C34IP40 数据表(HTML) 7 Page - Exar Corporation |
7 / 21 page 6-9 ST78C34 Rev. 3.00 written into the FIFO and the counter will not incre- ment. Two interrupt modes are available and are selected with the INTSEL pin. If this pin is tied low, a latched interrupt will result. In this mode, INT will transition low when a “1” is written to Control Register bit-0. A reset or reading the Status Register will clear the interrupt. If INTSEL pin is tied high, INT will transition low when a “1” is written to Control Register bit-0 and will transition high when a write to the parallel port is issued. This (non-latched) interrupt signal is always available in Status Register bit-6 regardless of the state of the INTSEL pin. Status Register bit-2 will always contain the latched interrupt state. The polarity of the INT pin may be inverted by setting Alternate Function Register bit-6 high. The ST78C34 provides additional programmable in- terrupt output options by programming the Alternate Function Register bit 4-5. INT output can be selected as FIFO full or FIFO empty interrupt. REGISTER DESCRIPTIONS PORT REGISTER Bi-directional printer port. Writing to this register during output mode will transfer the contents of the data bus to the PD7-PD0 ports . Reading this register during input mode will transfer the states of the PD7-PD0 to the data bus. This register will be set to the output mode after reset. PR BIT 7-0: PD7-PD0 bi-directional I/O ports. STATUS REGISTER This register provides the state of the printer outputs and the interrupt condition. STR BIT 1-0: This bits are set to “1” normally except when AFR bit 5-4 are both set to “1”. STR BIT-2: Interrupt condition. 0= an interrupt is pending This bit will be set to “0” at the falling edge of the -ACK input. 1= no interrupt is pending Reading the STATUS REGISTER will set this bit to “1”. STR BIT-3: ERROR input state. 0= ERROR input is in low state 1= ERROR input is in high state STR BIT-4: SLCT input state. 0= SLCT input is in low state 1= SLCT input is in high state STR BIT-5: PE input state. 0= PE input is in low state 1= PE input is in high state STR BIT-6: -ACK input state. 0= -ACK input is in low state 1= -ACK input is in high state STR BIT-7: BUSY or FIFO full signal. 0= BUSY input is in high state 1= BUSY input is in low state FIFO is enabled. 0= FIFO is full 1= One or more empty locations in FIFO COMMAND REGISTER The state of the -STROBE, -AUTOFDXT, INIT, - SLCTIN pins, and interrupt enable bit can be read by this register regardless of the I/O direction. COM BIT-0: -STROBE input pin. 0= -STROBE pin is in high state 1= -STROBE pin is in low state COM BIT-1: -AUTOFDXT input pin. 0= -AUTOFDXT pin is in high state 1= -AUTOFDXT pin is in low state |
类似零件编号 - ST78C34IP40 |
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类似说明 - ST78C34IP40 |
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