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HT56R22 Datasheet(PDF) 91 Page - Holtek Semiconductor Inc |
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HT56R22 Datasheet(HTML) 91 Page - Holtek Semiconductor Inc |
91 / 127 page HT56R22/HT56R23/HT56R24/HT56R25/HT56R26 Rev. 1.30 91 December 26, 2014 Multi-function Interrupt Within these devices there is a Multi-function interrupt. Unlike the other independent interrupts, these inter- rupts have no independent source, but rather are formed from other existing interrupt sources. A Multi-function interrupt request will take place when the Multi-function interrupt request flag, MFF is set. The Multi-function interrupt flag will be set when any of their included functions generate an interrupt request flag. To allow the program to branch to its respective in- terrupt vector address, when the Multi-function inter- rupt is enabled and the stack is not full, and either one of the interrupts contained the Multi-function interrupt oc- curs, a subroutine call to the Multi-function interrupt vec- tor will take place. When the interrupt is serviced, the Multi-Function request flag, will be automatically reset and the EMI bit will be automatically cleared to disable other interrupts. However, it must be noted that, although the Multi-function Interrupt flag will be automatically reset when the interrupt is serviced, the request flag from the original source of the Multi-function interrupt, will not be automatically reset and must be manually reset by the application program. Programming Considerations By disabling the interrupt enable bits, a requested inter- rupt can be prevented from being serviced, however, once an interrupt request flag is set, it will remain in this condition in the interrupt register until the corresponding interrupt is serviced or until the request flag is cleared by a software instruction. It is recommended that programs do not use the ²CALL subroutine ² instruction within the interrupt subroutine. Interrupts often occur in an unpredictable manner or need to be serviced immediately in some applications. If only one stack is left and the interrupt is not well con- trolled, the original control sequence will be damaged once a ²CALL subroutine² is executed in the interrupt subroutine. All of these interrupts have the capability of waking up the processor when in the Idle/Sleep Mode. Only the Program Counter is pushed onto the stack. If the contents of the register or status register are altered by the interrupt service program, which may corrupt the desired control sequence, then the contents should be saved in advance. LCD SCOM Function The devices have the capability of driving external LCD panels. The common pins for LCD driving, SCOM0~ SCOM3, are pin shared with certain pin on the PB0~ PB3 port. The LCD signals (COM and SEG) are gener- ated using the application program. LCD Operation An external LCD panel can be driven using this device by configuring the PB0~PB3 pins as common pins and using other output ports lines as segment pins. The LCD driver function is controlled using the SCOMC register which in addition to controlling the overall on/off function also controls the bias voltage setup function. This en- ables the LCD COM driver to generate the necessary VDD/2 voltage levels for LCD 1/2 bias operation. The SCOMEN bit in the SCOMC register is the overall master control for the LCD Driver, however this bit is used in conjunction with the COMnEN bits to select which Port B pins are used for LCD driving. Note that the Port Control register does not need to first setup the pins as outputs to enable the LCD driver operation. SCOMEN COMnEN Pin Function O/P Level 0 X I/O 0or1 1 0 I/O 0or1 1 1 SCOMN VDD/2 Output Control V D D S C O M 0 ~ S C O M 3 S C O M E N C O M n E N V D D / 2 S C O M o p e r a t i n g c u r r e n t LCD COM Bias |
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Similar Description - HT56R22_14 |
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