80C186EB/80C188EB Microprocessor User's Manual - CEUNES

CHIP-SELECT UNITRegister Name:Register Mnemonic:Register Function:Chip-Select Stop RegisterUCSSP, LCSSP, GCSxSP (x=0-7)Defines chip-select stop address and other controlfunctions.15 0CS9CS8CS7CS6CS5CS4CS3CS2CS1CS0CSENISTOPMEMRDYA1164-0ABitMnemonicBit NameResetStateFunctionCS9:0StopAddress3FFHDefines the ending address for the chip-select.CS9:0 are compared with the A19:10 (memorybus cycles) or A15:6 (I/O bus cycles) addressbits. A less than result enables the chip-select.CS9:0 are ignored if ISTOP is set.CSENChip-SelectEnable0(Note)Disables the chip-select when cleared. SettingCSEN enables the chip-select.ISTOPIgnore StopAddress0(Note)Setting this bit disables stop address checking,which automatically sets the ending address at0FFFFFH (memory) or 0FFFFH (I/O). WhenISTOP is cleared, the stop address requirementsmust be met to enable the chip-select.NOTE:Reserved register bits are shown with gray shading. Reserved bits must be writtento a logic zero to ensure compatibility with future Intel products. The reset state ofCSEN and ISTOP is ‘1’ for the UCSSP register.Figure 6-6. STOP Register Definition6-8