Sun Microsystems SPARCstation 20, Service Manual

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204 SPARCstation 20 Service Manual • July 1996
FIGURE B-5
SEC ASIC Functional Block Diagram
Clock Chip
The clock chip provides the MBus and SBus clocks for the system board and the
VSIMMs. There are 14 MBus clocks generated by the clock chip, one for each
receiver:
■
Four MBus clock receivers for each of two MBus modules (8 total)
■
One for the scalable memory controller (SMC)
■
One for the MBus-to-SBus interface (MSBI)
■
One for each pair of the eight memory SIMMs (4 total)
■
One for the SBus-to-external bus interface (SEC)
■
One for the SBus to DBRI Interface (DBRI)
■
One for the SBus to external data interface (MACIO)
■
One for SBus slots 0 and 1
■
One for SBus slots 2 and 3
Keyboard/
mouse chip
EEPROM
Diskette drive
chip
SEC ASIC
LED interface
Serial ports A/B
Keyboard/mouse
Diskette drive
Serial ports A/
B chip
NVRAM/TOD