Apple PowerBook 520 Technical Information download pdf (Page 27)

CHAPTER 2

Architecture

Input/Output Subsystem 13

Whitney Peripheral Support IC 2

The Whitney IC is a new Apple custom IC that provides the interface between the

system bus and the I/O bus that supports peripheral devices in the Macintosh

PowerBook 520 and 540 computers. The Whitney IC incorporates the following circuitry:

■ VIA1 cell

■ SWIM II cell

■ CPU ID register

The Whitney IC also performs the following functions:

■ bus error timing for I/O bus

■ bus arbitration for I/O bus

■ interrupt prioritization

■ VIA2 functions

■ sound data buffering

■ clock generation

■ power control signals

The Whitney IC contains the interface circuitry for the following peripheral ICs:

■ Combo, which is a combination of SCC and SCSI ICs

■ Singer, the sound codec IC

■ the Ethernet ID PROM

The Whitney IC provides the device select signals for the following ICs:

■ the Ethernet interface

■ the ﬂat panel display controller

■ the external video controller

The Whitney IC also provides the power off and reset signals to the peripheral

device ICs.

Power Manager IC 2

The Power Manager IC is a 68HC05 microprocessor that operates with its own RAM and

ROM. The Power Manager IC has the following functions:

■ controlling sleep, shutdown, and on/off modes

■ controlling power to the other ICs

■ controlling clock signals to the other ICs

■ supporting the ADB

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Apple PowerBook 520 Technical Information Page 27