System Architecture - Spectravideo SVI 318 Service – Technical Manual

TIIEOR Y OF OPERATION DESCRIPTIOR
4.

SYSTEM ARCHITECTURE

T he Spe c t rav ideo SVI-3 1 8 / SVI-328 and MarK II home compu t er is a
compu tat ional tool ba s e d on a Z i log BOA microcomputer system F igure 4-1.
The Zilog 80A microproces sor uni t ( � P ) provides cont ro l logic , data
manipu l a t ion and computat ion capabi lity to the SVI-3 1 8 / SVI-32 8 and Hark II
home compute r .
how the compute r is to pe r form .
in terp re te r is imp l emented as code store d in the sys tem ROM device s .
Temporary da ta and re s u l t s of comput a t ions can be stored in random-access
memory ( RAM ) .
Basic language p rogramme instruct ions and computationa l data .
Bit pa tterns i n ROM specify the type o f activi t y to be pe r forme d b y the
� P . The se ins truc t ions ( b it pat terns ) cause var ious ope ra t ions to be
pe r forme d .
( 1 ) Read the data at a spec i f ie d addre s s locat ion and place i t in an ./' P
reg i s te r .
Write the dat a f rom an�P register t o a speci f ie d addres sab l e
( 2 )
loca tion may be
( 3 ) Per form compu tat iona l or data compa r i son proc e du res on spec i f ie d data .
( 4 )
Jump or branch to a loca t ion other than t he next succes s ive memory
locat ion to re t rieve the next ins t ruct ion for programme execut ion .
The se jump or branch ope rat ions a re of t en determined by inte rrogat ing
the re su l t or s tatus of an ari thme t i c or log ica l computat iona l
operation .
( 5 ) Stop and wa i t for inte rrupt .
( 6 ) Branch to and return f rom subrou t ines .
(7 )
Branch to a vec tore d rout i ne to servic e inter rupt s and system res tart
opera tions .
The Zi log 80A
ROM dev i ce and per iphera l inter face device s such as PIO and VDP .
32K is dedicated for RAM devices (SOOOH - FFFFH in hexadeci ma l notation) .
The var ious e lemen t s that share the
a t t ribute s .
CPU ARCBIT!CTUU
A block diagram of the interna l arch itecture of the Z-80 CPU i s shown in
Figure 4-2 . The d iagram shows a l l of the major e l ements in the CPU and it
be
shou ld re ferred to th roughout the fol lowing descrip t ion .
The ./-' P uses contents of rea d-on l y memory ( ROM) to specify
Data in RAM can a l so be � P ins t r uct ions , but is more of ten
RAM,
VDP , PPI or PSG .
uses a 64K addre ss space .
�p
4.1
An Micro-Sof t Basic compu ter language
The lower 32K i s dedicated for
64K
address space pos s e ss unique
The upper