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HT37B90 Datasheet(PDF) 18 Page - Holtek Semiconductor Inc |
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HT37B90 Datasheet(HTML) 18 Page - Holtek Semiconductor Inc |
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18 / 80 page  HT37B90/HT37B70/HT37B50/HT37B30 Rev.1.00 18 June22,2017 BankPointer - RBP1,RBP2 The RAM Data Memory is divided into 8 Banks, known as Bank 0 to Bank 7. Selecting the required Data Memory area is achieved using the RAM Bank Pointers which are RBP1 and RBP2. The RBP1 and RBP2 match up with MP1 and MP2 respectively. If data in Bank 0 is to be ac- cessed, then the RBP registers must be loaded with the value ²00², while if data in Bank 1 is to be accessed, then the RBP registers must be loaded with the value ²01². Register IAR0 will always access data from Bank 0, irre- spective of the value of the Bank Pointer. The RBP1 and RBP2 register is located at memory location 60H in Bank 0 to Bank 7 and can only be accessed indirectly using two memory pointers MP1 and MP2 and the indi- rect addressing register IAR1 will always access data fromBank0toBank7. The Data Memory is initialized to Bank 0 after a reset, except for the WDT time-out reset in the Power Down Mode, in which case, the Data Memory bank remains unaffected. It should be noted that Special Function Data Memory is not affected by the bank selection, which means that the Special Function Registers can be accessed from within Bank 0 to Bank 7. Directly ad- dressing the Data Memory will always result in Bank 0 being accessed irrespective of the value of the Bank Pointer. Register BitNo. Function RBP1 0~2 RAMBankPoint1Select 000=SelectRAMBank0 001=SelectRAMBank1 010=SelectRAMBank2 011=SelectRAMBank3 100=SelectRAMBank4 101=SelectRAMBank5 110=SelectRAMBank6 111=SelectRAMBank7 3~4 Generalbits.Canwriteand read. 5~7 Unusedbit RBP1(04H) Register BitNo. Function RBP2 0~2 RAMBankPoint2Select 000=SelectRAMBank0 001=SelectRAMBank1 010=SelectRAMBank2 011=SelectRAMBank3 100=SelectRAMBank4 101=SelectRAMBank5 110=SelectRAMBank6 111=SelectRAMBank7 3~4 Generalbits.Canwriteand read. 5~7 Unusedbit RBP2(2FH) Note:UsingMP1orMP2areselectedby DACC.7. Accumulator - ACC The Accumulator is central to the operation of any microcontroller and is closely related with operations carried out by the ALU. The Accumulator is the place where all intermediate results from the ALU are stored. Without the Accumulator it would be necessary to write the result of each calculation or logical operation such as addition, subtraction, shift, etc., to the Data Memory resulting in higher programming and timing overheads. Data transfer operations usually involve the temporary storage function of the Accumulator; for example, when transferring data between one user defined register and another, it is necessary to do this by passing the data through the Accumulator as no direct transfer between tworegistersispermitted. ProgramCounterLowRegister - PCL To provide additional program control functions, the low byte of the Program Counter is made accessible to pro- grammers by locating it within the Special Purpose area of the Data Memory. By manipulating this register, direct jumps to other program locations are easily imple- mented. Loading a value directly into this PCL register will cause a jump to the specified Program Memory lo- cation, however, as the register is only 8-bit wide, only jumps within the current Program Memory page are per- mitted. When such operations are used, note that a dummycyclewillbeinserted. Look-upTableRegisters - TBLP1, TBMP1, TBHP1, TBLH These seven special function registers are used to con- trol operation of the look-up table which is stored in the Program Memory. TBLP1, TBMP1 and TBHP1 are the table pointer and indicate the location where the table data is located. Their value must be setup before any ta- ble read commands are executed. Their value can be changed, for example using the ²INC² or ²DEC² instruc- tions, allowing for easy table data pointing and reading. TBLH is the location where the high order byte of the ta- ble data is stored after a table read data instruction has been executed. Note that the lower order table data byte istransferredtoauserdefinedlocation. WatchdogTimerRegister - WDTS The Watchdog feature of the microcontroller provides an automatic reset function giving the microcontroller a means of protection against spurious jumps to incorrect Program Memory addresses. To implement this, a timer is provided within the microcontroller which will issue a reset command when its value overflows. To provide variable Watchdog Timer reset times, the Watchdog Timer clock source can be divided by various division ra- tios, the value of which is set using the WDTS register. By writing directly to this register, the appropriate divi- sion ratio for the Watchdog Timer clock source can be |
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