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HT95A400 Datasheet(PDF) 7 Page - Holtek Semiconductor Inc |
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HT95A400 Datasheet(HTML) 7 Page - Holtek Semiconductor Inc |
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7 / 48 page  HT95AXXX Rev. 1.20 7 May 26, 2004 Program Memory - ROM The program memory is used to store the program in- structions which are to be executed. It also contains data, table, and interrupt entries, and is organized into 8K ´16 bits´2 banks (HT95A400/40P), 8K´16 bits (HT95A300/30P) or 4K ´16 bits (HT95A200/20P, HT95A100/10P), addressed by the program counter and table pointer. For the HT95A400/40P, the program memory is divided into 2 banks, each bank having a ROM Size 8Kx16its. To move from the present ROM bank to a different ROM bank, the higher 1 bits of the ROM address are set by the BP (Bank Pointer), while the remaining 13 bits of the PC are set in the usual way by executing the appropriate jump or call instruction. As the 14 address bits are latched during the execution of a call or jump instruction, the correct value of the BP must first be setup before a jump or call is executed. When either a software or hard- ware interrupt is received, note that no matter which ROM bank the program is in, the program will always jump to the appropriate interrupt service address in Bank 0. The original 14 bits address will be stored on the stack and restored when the relevant RET/RETI instruc- tion is executed, automatically returning the program to the original ROM bank. This eliminates the need for pro- grammers to manage the BP when interrupts occur. Certain locations in the program memory are reserved for special usage: · Location 0000H (Bank0) This area is reserved for the initialization program. Af- ter chip power-on reset or external reset or WDT time-out reset, the program always begins execution at location 0000H. · Location 0004H (Bank0) This area is reserved for the external interrupt service program. If the INT input pin is activated, the external interrupt is enabled and the stack is not full, the pro- gram begins execution at location 0004H. · Location 0008H (Bank0) This area is reserved for the Timer/Event Counter 0 interrupt service program. If a timer interrupt results from a Timer/Event Counter 0 overflow, the Timer/Event Counter 0 interrupt is enabled and the stack is not full, the program begins execution at loca- tion 0008H. · Location 000CH (Bank0) This location is reserved for the Timer/Event Counter 1 interrupt service program. If a timer interrupt results from a Timer/Event Counter 1 overflow, the Timer/Event Counter 1 interrupt is enabled and the stack is not full, the program begins execution at loca- tion 000CH. · Location 0014H (Bank0) This location is reserved for real time clock (RTC) in- terrupt service program. When RTC generator is en- abled and time-out occurs, the RTC interrupt is enabled and the stack is not full, the program begins execution at location 0014H. · Location 0018H (Bank0) This location is reserved for the HKS pin edge transi- tion or HDI pin falling edge transition or HFI pin rising edge transition. If this condition occurs, the dialer I/O interrupt is enabled and the stack is not full, the pro- gram begins execution at location 18H. Table Location Any location in the ROM space can be used as look-up tables. The instructions ²TABRDC [m]² (the current page, one page=256 words) and ²TABRDL [m]² (the last page) transfer the contents of the lower-order byte to the specified data memory, and the higher-order byte to TBLH (08H). For the HT95A400/40P, the instruction ²TABRDC [m]² is used for any page of any bank. Only the destination of the lower-order byte in the table is well-defined, and the higher-order byte of the table word is transferred to TBLH. The table pointer (TBLP) or (TBHP, TBLP for the HT95A400/40P) is a read/write register (07H) or (1FH, 07H for the HT95A400/40P), which indicates the table location. Before accessing the table, the location must be placed in the (TBLP) or (TBHP, TBLP for the HT95A400/40P). The TBLH is read only and cannot be restored. If the main routine and the 0 0 0 H 0 0 4 H 0 0 8 H D e v i c e I n i t i a l i z a t i o n P r o g r a m E x t e r n a l I n t e r r u p t S u b r o u t i n e T i m e r / E v e n t C o u n t e r 0 I n t e r r u p t S u b r o u t i n e P r o g r a m R O M 1 6 b i t s L o o k - u p T a b l e ( 2 5 6 W o r d s ) 1 0 0 H L o o k - u p T a b l e ( 2 5 6 W o r d s ) ( L a s t P a g e s ) N o t e : T h e L a s t p a g e f o r H T 9 5 A 4 0 0 / 4 0 P i s 3 F 0 0 H ~ 3 F F F H T h e L a s t p a g e f o r H T 9 5 A 3 0 0 / 3 0 P i s 1 F 0 0 H ~ 1 F F F H T h e L a s t p a g e f o r H T 9 5 A 2 0 0 / 2 0 P i s 0 F 0 0 H ~ 0 F F F H T h e L a s t p a g e f o r H T 9 5 A 1 0 0 / 1 0 P i s 0 F 0 0 H ~ 0 F F F H 1 F F H T i m e r / E v e n t C o u n t e r 1 I n t e r r u p t S u b r o u t i n e 0 0 C H 0 1 0 H R T C I n t e r r u p t S u b r o u t i n e 0 1 4 H D i a l e r I / O I n t e r r u p t S u b r o u t i n e 0 1 8 H R e s e r v e d Program Memory |
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