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P89CE558 Datasheet(PDF) 9 Page - NXP Semiconductors |
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P89CE558 Datasheet(HTML) 9 Page - NXP Semiconductors |
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9 / 72 page  Philips Semiconductors Preliminary specification P83CE558/P80CE558/P89CE558 Single-chip 8-bit microcontroller 1996 Aug 06 9 6.2.1 Program Memory The program memory of the P8xCE558 consists of 32 Kbytes ROM respectively FEEPROM (”Flash Memory”) on-chip, externally expandable up to 64 Kbytes. If, during RESET, the EA pin was held HIGH, the P8xCE558 executes out of the internal program memory unless the address exceeds 7FFFH. Locations 8000H through 0FFFFH are then fetched from the external program memory. If the EA pin was held LOW during RESET the P8xCE558 fetches all instructions from the external program memory. The EA input is latched during RESET and is don’t care after RESET. The internal program memory content is protected, by setting a mask programmable security bit (ROM) or by the software programmable security byte (FEEPROM) respectively, i.e. it cannot be read out at any time by any test mode or by any instruction in the external program memory space. The MOVC instructions are the only ones which have access to program code in the internal or external program memory. The EA input is latched during RESET and is ’don’t care’ after RESET. This implementation prevents from reading internal program code by switching from external program memory to internal program memory during MOVC instruction or an instruction that handles immediate data. Table 1 lists the access to the internal and external program memory with MOVC instructions when the security feature has been activated. 6.2.2 Internal Data Memory The internal data memory is divided into three physically separated parts: 256 bytes of RAM, 768 bytes of AUX-RAM, and a 128 bytes special function area. These can be addressed each in a different way (see also Table 2). – RAM 0 to 127 can be addressed directly and indirectly as in the 80C51. Address pointers are R0 and R1 of the selected registerbank. – RAM 128 to 255 can only be addressed indirectly. Address pointers are R0 and R1 of the selected registerbank. – AUX-RAM 0 to 767 is also indirectly addressable as external DATA MEMORY locations 0 to 767 via MOVX-Datapointer instruction, unless it is disabled by setting ARD = 1. AUX-RAM 0 to 767 is indirectly addressable via pageregister (XRAMP) and MOVX-Ri instructions, unless it is disabled by setting ARD = 1 (see Figure 5). When executing from internal program memory, an access to AUX-RAM 0 to 767 will not affect the ports P0, P2, P3.6 and P3.7. An access to external DATA MEMORY locations higher than 767 will be performed with the MOVX @ DPTR instructions in the same way as in the 80C51 structure, so with P0 and P2 as data/address bus and P3.6 and P3.7 as write and read timing signals. Note that the external DATA MEMORY cannot be accessed with R0 and R1 as address pointer if the AUX-RAM is enabled (ARD = 0, default). – The Special Function Registers (SFR) can only be addressed directly in the address range from 128 to 255 (see Table 5). – Four register banks, each 8 registers wide, occupy locations 0 through 31 in the lower RAM area. Only one of these banks may be enabled at a time. The next 16 bytes, locations 32 through 47, contain 128 directly addressable bit locations.The stack can be located anywhere in the internal 256 bytes RAM.The stack depth is only limited by the available internal RAM space of 256 bytes (see Figure 7). All registers except the program counter and the four register banks reside in the Special Function Register address space. Table 1. Memory Access by the MOVC Instruction for Protected ROMs MOVC LOCATION ACCESS TO INTERNAL PROGRAM MEMORY ACCESS TO EXTERNAL PROGRAM MEMORY MOVC in internal program memory YES YES MOVC in external program memory NO YES NOTE: 1. If the security feature has not been activated, there are no restrictions for MOVC instructions. Table 2. Internal Data Memory Map LOCATION ADDRESSED RAM 0 to 127 Direct and indirect AUX-RAM 0 to 767 Indirect only with MOVX RAM 128 to 255 Indirect only SFR 128 to 255 Direct only |
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