Overview Of Chip Selection Facility - Fujitsu MB90480 Series Hardware Manual

CHAPTER 20 CHIP SELECTION FACILITY

20.1 Overview of Chip Selection Facility

The chip selection facility is a module used to generate a chip selection signal for
simplified memory connection to the outside. It contains four chip selection output
pins. The chip selection facility has four chip select output pins and enables an area
within the hardware to be specified via an output setting register, and if the device
detects an access to that external address, it outputs a selection signal via the
corresponding pin.
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Overview of the chip selection facility
The chip selection facility contains two 8-bit registers for each output pin. One register (CARx) is
used to specify the upper 8 bits of the compared address, allowing area within 64 K bytes to be
specified. Another register (CMRx) is used to mask the corresponding bits of the compared
address so that values above 64 K bytes can be specified for the area to be detected.
In external bus hold mode, CS output is set to high impedance mode.
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