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68901P05 Datasheet(PDF) 4 Page - STMicroelectronics |
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68901P05 Datasheet(HTML) 4 Page - STMicroelectronics |
4 / 33 page Figure 4 : Register Map. Address Port N °. Abbreviation Regi ster N ame 0 1 2 GPIP AER DDR GENERAL PURPOSE I/O ACTIVE EDGE REGISTER DATA DIRECTION REGISTER 3 4 5 6 7 8 9 A B IERA IERB IPRA IPRB ISRA ISRB IMRA IMRB VR INTERRUPT ENABLE REGISTER A INTERRUPT ENABLE REGISTER B INTERRUPT PENDING REGISTER A INTERRUPT PENDING REGISTER B INTERRUPT IN-SERVICE REGISTER A INTERRUPT IN-SERVICE REGISTER B INTERRUPT MASK REGISTER A INTERRUPT MASK REGISTER B VECTOR REGISTER C D E F 10 11 12 TACR TBCR TCDCR TADR TBDR TCDR TDDR TIMER A CONTROL REGISTER TIMER B CONTROL REGISTER TIMERS C AND D CONTROL REGISTER TIMER A DATA REGISTER TIMER B DATA REGISTER TIMER C DATA REGISTER TIMER D DATA REGISTER 13 14 15 16 17 SCR UCR RSR TSR UDR SYNC CHARACTER REGISTER USART CONTROL REGISTER RECEIVER STATUS REGISTER TRANSMITTER STATUS REGISTER USART DATA REGISTER INTERRUPTS The General Purpose I/O-Interrupt Port (GPIP) pro- vides eight I/O lines that may be operated either as inputs or outputs under software control. In addition, each line may generate an interrupt in either a po- sitive going edge or a negative going edge of the in- put signal. The GPIP has three associated registers. One al- lows the programmer to specify the Active Edge for each bit that will trigger an interrupt. Another register specifies the Data Direction (input or output) asso- ciated with each bit. The third register is the actual data I/O register used to input or output data to the port. These three registers are illstrated in figure 5. The Active Edge Register (AER) allows each of the General Purpose Interrupts to provide an interrupt on either a 1-0 transition or a 0-1 transition. Writing a zero to the appropriate bit of the AER causes the associated input to produce an interrupt on the 1-0 transition. The edge bit is simply one input to an ex- clusive-or gate, with the other input coming from the input buffer ant the output going to a 1-0 transition detector. Thus, depending upon the state of the in- put, writing the AER can cause an interrupt-produ- cing transition, which will cause an interrupt on the associated channel, if that channel is enabled. One would then normally configure the AER before enabling interrupts via IERA and IERB. Note : Changing the edge bit, with the interrupt enabled, may cause an interrupt on that channel. The Data Direction Register (DDR) is used to define 10-17 as inputs or as outputs on a bit by bit basis. Writing a zero into a bit of the DDR causes the cor- responding Interrupt-I/O pin to be a Hi-Z input. Wri- ting a one into a bit of the DDR causes the cor- responding pin to be configured as a push-pull out- put. When data is written into the GPIP, those pins defined as inputs will remain in the Hi-Z state while those pins defined as outputs will assume the state (high or low) of their corresponding bit in the GPIP. When the GPIP is read, the data read will come di- rectly from the corresponding bit of the GPIPregister for all pins defined as output, while the data read on all pins defined as inputs will come from the input buffers. Each individual function in the MK68901 is provided with a unique interrupt vector that is presented to the system during the interrupt acknowledge cycle. The interrupt vector returned during the interrupt ac- knowledge cycle is shown in figure 6, while the vec- tor register is shown in figure 7. MK68901 4/33 |
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