Compaq AlphaServer DS20 Service Manual download pdf (Page 79)

Error Registers 3-9

3.5

Miscellaneous Register (MISC)

This register is designed so that only writes of 1 affect it. When a 1 is written to

any bit in the register, the programmer does not need to be concerned with read-

modify-write or the status of any other bits in the register. Once NXM is set, the

NXS field is locked. It is unlocked when software clears the NXM field. The

ABW (arbitration won) field is locked if either ABW bit is set, so the first CPU to

write it locks out the other CPU. Writing a 1 to ACL (arbitration clear) clears

both ABW bits and both ABT (arbitration try) bits and unlocks the ABW field.

Address 801 A000 0040

Access RW

PK1417-99

31 43

44 43 40 39

29 28 27 25 24 23 20 19 16 15 12 11 8 7 2 1

reserved

DEVSUP

REV

NXS

000

NXM

ACL

ABT

ABW

IPREQ

IPINTR

ITINTR

CPUID

1 2 ... 74 75 76 77 78 79 80 81 82 83 84 ... 181 182

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Compaq AlphaServer DS20 Service Manual Page 79