Sun Microsystems SPARCstation 20, Service Manual

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Appendix B Functional Description 203
FIGURE B-4
MACIO ASIC Functional Block Diagram
SBus-to-External Bus Interface
The SBus-to-external bus interface (SEC) ASIC provides the interface between the
SBus and the external bus. The external bus connects to the following:
■
Serial port chips (2)
■
Audio chip
■
Diskette drive controller
■
4-Mbit EEPROM
■
NVRAM/TOD chip
■
LED interface
One of the serial port chips provides serial ports A and B. The second serial port
chip provides the keyboard and mouse port. Line drivers interface the two serial
port chips to the serial ports.
FIGURE B-5
illustrates a functional block diagram of the
SEC ASIC.
DMA
LANCE
Parallel
port
SCSI
Fast
SCSI
controller
AUI
TPE
Clock
chip
Parallel
port
SBus
MACIO ASIC