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HT49CA1 Datasheet(PDF) 9 Page - Holtek Semiconductor Inc |
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HT49CA1 Datasheet(HTML) 9 Page - Holtek Semiconductor Inc |
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9 / 57 page  HT49RA1/HT49CA1 Rev. 1.10 9 March 30, 2014 · Location 00CH This internal vector is used by the Timer/Event Coun- ter 0. If a counter overflow occurs, the program will jump to this location and begin execution if the timer/event counter interrupt is enabled and the stack is not full. · Location 010H This internal vector is used by the Timer/Event Coun- ter 1. If a counter overflow occurs, the program will jump to this location and begin execution if the timer/event counter interrupt is enabled and the stack is not full. · Location 014H This internal vector is used by the Time Base interrupt. If a Time Base interrupt occurs, the program will jump to this location and begin execution if the time base in- terrupt is enabled and the stack is not full. · Location 018H This internal vector is used by the Real Time Clock in- terrupt. The program will jump to this location and be- gin execution when a Real Time Clock interrupt signal is generated if the interrupt is enabled and the stack is not full. Look-up Table Any location within the Program Memory can be defined as a look-up table where programmers can store fixed data. To use the look-up table, the table pointer must first be setup by placing the lower order address of the look up data to be retrieved in the table pointer register, TBLP. This register defines the lower 8-bit address of the look-up table. After setting up the table pointer, the table data can be retrieved from the current Program Memory page or last Program Memory page using the ²TABRDC[m]² or ²TABRDL [m]² instructions, respectively. When these in- structions are executed, the lower order table byte from the Program Memory will be transferred to the user de- fined Data Memory register [m] as specified in the in- struction. The higher order table data byte from the Program Memory will be transferred to the TBLH special register. Any unused bits in this transferred higher order byte will be read as ²0². The following diagram illustrates the addressing/data flow of the look-up table: Table Program Example The following example shows how the table pointer and table data is defined and retrieved from the HT49RA1 microcontroller. This example uses raw table data lo- cated in the last page which is stored there using the ORG statement. The value at this ORG statement is ²F00H² which refers to the start address of the last page within the 4K Program Memory of the HT49RA1 microcontroller. The table pointer is setup here to have an initial value of ²06H². This will ensure that the first data read from the data table will be at the Program Memory address ²F06H² or 6 locations after the start of the last page. Note that the value for the table pointer is referenced to the first address of the present page if the ²TABRDC [m]² instruction is being used. The high byte of the table data which in this case is equal to zero will be transferred to the TBLH register automatically when the ²TABRDL [m]² instruction is executed. Because the TBLH register is a read-only register and cannot be restored, care should be taken to ensure its protection if both the main routine and Interrupt Service Routine use table read instructions. If using the table read instructions, the Interrupt Service Routines may change the value of the TBLH and subsequently cause errors if used again by the main routine. As a rule it is recommended that simultaneous use of the table read instructions should be avoided. However, in situations where simultaneous use cannot be avoided, the inter- rupts should be disabled prior to the execution of any main routine table-read instructions. Note that all table related instructions require two instruction cycles to complete their operation. Instruction Table Location Bits b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0 TABRDC [m] PC11 PC10 PC9 PC8 @7 @6 @5 @4 @3 @2 @1 @0 TABRDL [m] 1111 @7 @6 @5 @4 @3 @2 @1 @0 Table Location Note: PC11~PC8: Current Program Counter bits @7~@0: Table Pointer TBLP bits The table address location is 12 bits, i.e. from b11~b0. P r o g r a m M e m o r y P r o g r a m C o u n t e r H i g h B y t e T B L P T B L H S p e c i f i e d b y [ m ] T a b l e C o n t e n t s H i g h B y t e T a b l e C o n t e n t s L o w B y t e |
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