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5962H9563801VYC Datasheet(PDF) 3 Page - Aeroflex Circuit Technology |
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5962H9563801VYC Datasheet(HTML) 3 Page - Aeroflex Circuit Technology |
3 / 19 page 3 RST: Reset Input. A high on this input for 24 oscillator periods while the oscillator is running resets the device. All ports and SFRs reset to their default conditions. Internal data memory is undefined after reset. Program execution begins within 12 oscillator periods (one machine cycle) after the RST signal is brought low. RST contains an internal pulldown resistor to allow implementing power-up reset with only an external capacitor. ALE: Address Latch Enable. The ALE output is a pulse for latching the low byte of the address during accesses to external memory. In normal operation, the ALE pulse is output every sixth oscillator cycle and may be used for external timing or clocking. However, during each access to external Data Memory (MOVX instruction), one ALE pulse is skipped. PSEN: Program Store Enable. This active low signal is the read strobe to the external program memory. PSEN activates every sixth oscillator cycle except that two PSEN activations are skipped during external data memory accesses. EA: External Access Enable. This pin should be strapped to VSS (Ground) for the UT69RH051. XTAL1: Input to the inverting oscillator amplifier. XTAL2: Output from the inverting oscillator amplifier. 2.1 Hardware/Software Interface 2.1.1 Memory The UT69RH051 has a separate address space for Program and Data Memory. Internally, the UT69RH051 contains 256 bytes of Data Memory. It addresses up to 64Kbytes of external Data Memory and 64Kbytes of external Program Memory. 2.1.1.1 Program Memory There is no internal program memory in the UT69RH051. All program memory is accessed as external through ports P0 and P2. The EA pin must be tied to VSS (ground) to enable access to external locations 0000H through 7FFFH. Following reset, the UT69RH051 fetches the first instruction at address 0000h. 2.1.1.2 Data Memory The UT69RH051 implements 256 bytes of internal data RAM. The upper 128 bytes of this RAM occupy a parallel address space to the SFRs. The CPU determines if the internal access to an address above 7FH is to the upper 128 bytes of RAM or to the SFR space by the addressing mode of the instruction. If direct addressing is used, the access is to the SFR space. If indirect addressing is used, the access is to the internal RAM. Stack operations are indirectly addressed so the upper portion of RAM can be used as stack space. Figure 3 shows the organization of the internal Data Memory. The first 32 bytes are reserved for four register banks of eight bytes each. The processor uses one of the four banks as its working registers depending on the RS1 and RS0 bits in the PSW SFR. At reset, bank 0 is selected. If four register banks are not required, use the unused banks as general purpose scratch pad memory. The next 16 bytes (128 bits) are individually bit addressable. The remaining bytes are byte addressable and can be used as general purpose scratch pad memory. For addresses 0 - 7FH, use either direct or indirect addressing. For addresses larger than 7FH, use only indirect addressing. In addition to the internal Data Memory, the processor can access 64Kbytes of external Data Memory. The MOVX instruction accesses external Data Memory. 2.1.2 Special Function Registers Table 3 contains the SFR memory map. Unoccupied addresses are not implemented on the device. Read accesses to these addresses will return unknown values and write accesses will have no effect. |
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