Intel Embedded Microcontroller, 8XC251SA, 8XC251SP manual Configuration Byte Location Selector Ucon

DEVICE CONFIGURATION

4.4CONFIGURATION BYTE LOCATION SELECTOR (UCON)

The Configuration Byte Location Selector (UCON) applies only to OTPROM and EPROM prod- ucts. In conjunction with EA#, UCON specifies whether the configuration array is accessed from on-chip memory or external memory.

If the UCON bit is clear (e.g., UCON=0), the configuration array is fetched from on-chip nonvol- atile memory at addresses FF:FFF8H to FF:FFFFH. The configuration bytes are located at loca- tions FF:FFF8H and FF:FFF9H.

If UCON is set (e.g., UCON=1), the state of the EA# pin at device reset determines whether the configuration array is accessed from on-chip memory or external memory. If EA# is connected to VCC, the configuration array is accessed from on-chip nonvolatile memory at addresses FF:FFF8H through FF:FFFFH (same as for UCON=0). If EA# is connected to VSS, the configu- ration array is obtained from external memory (e.g., a 27512 EPROM).

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