HP 3562A, Service Manual

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C I RC U I T D E SCRI PTIONS MOD E L 3562A
6-8 A7 FLOATING POINT PROCESSOR
(Refer to figure 6-A7) The Floati ng Point Processor (FPP) is a fast arithmetic u n it which
carries out real and com plex arithmetic operations on blocks of d ata stored in the
A8 Global RAM. The processing u n its (AL U s) of the FPP are six AM2903 bit-sl ice micro­
p rocessor ICs. I nstru ctions are provided to the ALUs by an add ress sequencer and seven
m i crocode PROMs.
The FPP can perform 85 u n ique operations i ncluding add ition, subtraction, m u ltiplication,
and division. Operations are performed on data blocks which have been normal ized and
stored in the A8 G lobal RAM. The data can have one of three formats:
•
2's complem ent integer (1 6 bit)
•
Si ngle prec ision floati ng poi nt (32 bit)
•
Double prec ision floating poi nt (64 bit)
The operation the FPP performs on a data block is d ictated by the A2 System CPU. The
system CPU sets up a command stack in the global RAM to tel l the FPP which operation
to perform. A com mand stack consists of the fo llowing:
•
32 b it command word (add, sub, etc.)
•
N u m ber of entries in the data block which are to be operated on.
•
Constants to i n d icate if the data block is real or complex.
•
The beginning add ress of the data block in global RAM.
•
The desti nation address of the res u lts.
Commands may be executed individu a l ly or in groups. Commands in groups are executed
i n series and can i n c l ude m u ltiple looping.
To an operation, the FPP
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6-58
IS an overvIew an FPP operation:
1 . The system CPU puts a command stack or series of com mand stacks in the global RAM.
2 . The system CPU add resses the F P P using the system add ress b u s and puts the starting
add ress of the command stack on the system data bus.
3. The FPP recogn izes that it has been add ressed (AD DFLG) by the C P U .
4 . The ALUs read the comm and stack's add ress that is now i n the command pointer
registers and on the B bus. The add ress of the command stack is stored in the i nternal
registers of the ALUs.