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ST63142 数据表(PDF) 15 Page - STMicroelectronics |
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ST63142 数据表(HTML) 15 Page - STMicroelectronics |
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15 / 86 page  D7-D2. These bits are not used. PRPR1-PRPR0. These are the program ROM banking bits and the value loaded selects the cor- responding page to be addressed in the lower part of 4K program address space as specified in Table 3. This register is undefined on reset. Note: Only the lower part of address space has been bankswitched because interrupt vectors and com- mon subroutines should be available all the time. The reason of this structure is due to the fact that it is not possible to jump from a dynamic page to an- other, unless jumping back to the static page, changing contents of PRPR, and, then, jumping to a different dynamic page. PRPR1 PRPR0 PC11 Memory Page X X 1 Static Page (Page1) 0 0 0 Page 0 0 1 0 Page 1 (Static Page) 1 0 0 Page 2 1 1 0 Page 3 Table 3. Program ROM Page Register Coding Care is required when handling the PRPR as it is write only. For this reason, it is not allowed to change the PRPR contents while executing inter- rupts drivers, as the driver cannot save and than restore its previous content. Anyway, this opera- tion may be necessary if the sum of common rou- tines and interrupt drivers will take more than 2K bytes; in this case could be necessary to divide the interrupt driver in a (minor) part in the static page (start and end), and in the second (major) part in one dynamic page. If it is impossible to avoid the writing of this register in interrupts drivers, an im- age of this register must be saved in a RAM loca- tion, and each time the program writes the PRPR it writes also the image register. The image register must be written first, so if an interrupt occurs be- tween the two instructions the PRPR is not af- fected. MEMORY SPACES (Continued) PRPR Program ROM Page Register (CAh, Write Only) D7 D6 D5 D4 D3 D2 D1 D0 PRPR0 = PROG.ROM Select 0 PRPR1 = PROG.ROM Select 1 UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED Figure 11. Program ROM Page Register ROM Page Device Address Device Address (1) Description PAGE 0 0000h-007Fh 0080h-07FFh 0000h-007Fh 0080h-07FFh Reserved User ROM PAGE 1 “STATIC” 0800h-0F9Fh 0FA0h-0FEFh 0FF0h-0FF7h 0FF8h-0FFBh 0FFCh-0FFDh 0FFEh-0FFFh 0800h-0F9Fh 0FA0h-0FEFh 0FF0h-0FF7h 0FF8h-0FFBh 0FFCh-0FFDh 0FFEh-0FFFh User ROM Reserved Interrupt Vectors Reserved NMI Vector Reset Vector PAGE 2 0000h-000Fh 0010h-07FFh 1000h-100Fh 1010h-17FFh Reserved User ROM PAGE 3 0000h-000Fh 0010h-07FFh 1800h-180Fh 1810h-1FFFh Reserved User ROM Table 4. ST631xx Program ROM Map Note 1. EPROM addresses relate to the use of ST63E1xx EPROM Emulation device. This register is undefined on reset. Neither read nor single bit instructions may be used to address this register. ® ST63140,142,126,156 11/82 |
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