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HT56R22 Arkusz danych(PDF) 46 Page - Holtek Semiconductor Inc |
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HT56R22 Arkusz danych(HTML) 46 Page - Holtek Semiconductor Inc |
46 / 127 page HT56R22/HT56R23/HT56R24/HT56R25/HT56R26 Rev. 1.30 46 December 26, 2014 I/O Pin Structures The diagrams illustrate the I/O pin internal structures. As the exact logical construction of the I/O pin may differ from these drawings, they are supplied as a guide only to assist with the functional understanding of the I/O pins. Programming Considerations Within the user program, one of the first things to con- sider is port initialisation. After a reset, the I/O data reg- ister and I/O port control register will be set high. This means that all I/O pins will default to an input state, the level of which depends on the other connected circuitry and whether pull-high options have been selected. If the port control registers, are then programmed to setup some pins as outputs, these output pins will have an ini- tial high output value unless the associated port data register is first programmed. Selecting which pins are in- puts and which are outputs can be achieved byte-wide by loading the correct value into the port control register or by programming individual bits in the port control reg- ister using the ²SET [m].i² and ²CLR [m].i² instructions. Note that when using these bit control instructions, a read-modify-write operation takes place. The microcontroller must first read in the data on the entire port, modify it to the required new bit values and then re- write this data back to the output ports. Pins PA0 to PA7 each have a wake-up functions, se- lected via the PAWK register. When the device is in the Idle/Sleep Mode, various methods are available to wake the device up. One of these is a high to low transition of any of the these pins. Single or multiple pins on Port A can be setup to have this function. Timer/Event Counters The provision of timers form an important part of any microcontroller, giving the designer a means of carrying out time related functions. The devices contain several 8-bit and 16-bit count-up timers. As each timer has three different operating modes, they can be configured to op- erate as a general timer, an external event counter or as a pulse width measurement device. The provision of a prescaler to the clock circuitry of the 8-bit Timer/Event Counter also gives added range to this timer. There are two types of registers related to the Timer/Event Counters. The first are the registers that contain the actual value of the Timer/Event Counter and into which an initial value can be preloaded. Reading from these registers retrieves the contents of the Timer/Event Counter. The second type of associated register is the Timer Control Register which defines the timer options and determines how the Timer/Event Counter is to be used. The Timer/Event Counters can have the their clock configured to come from an internal clock source. In addition, their clock source can also be configured to come from an external timer pin. T 1 T 2 T 3 T 4 T 1 T 2 T 3 T 4 W r i t e t o P o r t R e a d f r o m P o r t S y s t e m C l o c k P o r t D a t a Read Modify Write Timing V D D M U X R e a d D a t a R e g i s t e r C o n t r o l B i t P u l l - H i g h S e l e c t D a t a B u s W r i t e C o n t r o l R e g i s t e r C h i p R e s e t R e a d C o n t r o l R e g i s t e r W r i t e D a t a R e g i s t e r D a t a B i t P B 0 / S C O M 0 ~ P B 3 / S C O M 3 V D D / 2 W e a k P u l l - u p D Q C K S Q D Q C K S Q C O M n E N S C O M E N PB Input/Output Port |
Podobny numer części - HT56R22_14 |
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Podobny opis - HT56R22_14 |
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