Lenovo ThinkPad 770X Technical Reference Manual for the ThinkPad 770 - Page 42
RT/CMOS Address and NMI Mask Register (Hex 0070), RT/CMOS Data Register (Hex 0071), RT/CMOS RAM bytes.
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RT/CMOS Address and NMI Mask Register (Hex 0070) The NMI mask register is used with the RT/CMOS data register (hex 0071) to read from and write to the RT/CMOS RAM bytes. Attention The operation following a write to hex 0070 should access hex 0071; otherwise, intermittent failures of the RT/CMOS RAM can occur. Bit Function 7 NMI mask 6-0 RT/CMOS RAM address Figure 2-13. RT/CMOS Address and NMI Mask Register (Hex 0070) Bit 7 Bits 6-0 When this write-only bit is set to 1, the NMI is masked (disabled). This bit is set to 1 by a power-on reset. These bits are used to select RT/CMOS RAM addresses. RT/CMOS Data Register (Hex 0071) The RT/CMOS data register is used with the RT/CMOS address and NMI mask register (hex 0070) to read from and write to the RT/CMOS RAM bytes. Bit Function 7-0 RT/CMOS data Figure 2-14. RT/CMOS Data Register (Hex 0071) 2-20 System Board