PERIPHERAL CONTROL BLOCK

As an example, to relocate the Peripheral Control Block to the memory range 10000-100FFH, the user would program the PCB Relocation Register with the value 1100H. Since the Relocation Register is part of the Peripheral Control Block, it relocates to word 10000H plus its fixed offset.

NOTE

Due to an internal condition, external ready is ignored if the device is configured in Cascade mode and the Peripheral Control Block (PCB) is located at 0000H in I/O space. In this case, wait states cannot be added to interrupt acknowledge bus cycles. However, you can add wait states to interrupt acknowledge cycles if the PCB is located at any other address.

4.5.1Considerations for the 80C187 Math Coprocessor Interface

Systems using the 80C187 math coprocessor interface must not relocate the Peripheral Control Block to location 0000H in I/O space. The 80C187 interface uses I/O locations 0F8H through 0FFH. If the Peripheral Control Block resides in these locations, the processor communicates with the Peripheral Control Block, not the 80C187 interface circuitry.

NOTE

If the PCB is located at 0000H in I/O space and access to the math coprocessor interface is enabled (the Escape Trap bit is clear), a numerics (ESC) instruction causes indeterminate system operation.

Since the 8-bit bus version of the device does not support the 80C187, it automatically traps an ESC instruction to the Type 7 interrupt, regardless of the state of the Escape Trap (ET) bit.

For details on the math coprocessor interface, see Chapter 11, “Math Coprocessing.”

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Intel 80C188XL, 80C186XL user manual Considerations for the 80C187 Math Coprocessor Interface