DATA 620/i SYSTEM REFERENCE MANUAL . - Al Kossow's Bitsavers
DATA 620/i SYSTEM REFERENCE MANUAL . - Al Kossow's Bitsavers
DATA 620/i SYSTEM REFERENCE MANUAL . - Al Kossow's Bitsavers
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W bus. The memory word (W) register is directly connected<br />
to all memory modules through the W bus. The bus is<br />
bidirectional and time-shared among memory modules.<br />
L bus. The memory address (L) register is directly connected<br />
to all memory modules through the L bus. The bus is<br />
unidirectional.<br />
2.1.5 Input/Output Bus<br />
The standard <strong>DATA</strong> <strong>620</strong>/i is provided with a bidirectional<br />
input/output (I/O) bus that permits programmed data transfers<br />
between periphera I devi ces and the computer.<br />
2.1.6 Memory<br />
The internal storage of the computer consists of 4096-word<br />
modules connected to the Land W buses. The mainframe<br />
can accommodate one 4096-word module. Additiona I<br />
modules are added in an additional frame that is attached to<br />
the mainframe. The computer memory can be expanded to<br />
a maximum of 32,768 words using 4096-word modules.<br />
I nstruction words read from memory are transferred to the<br />
control section for execution. Words may be transferred,<br />
under program control, from memory to the arithmetic/logic<br />
section, to the operational registers, or to the I/O bus.<br />
Words may be transferred, under program control, to memory<br />
from the operational registers or the I/O bus. When the<br />
direct memory access option is used, the system is capable<br />
of direct transfer between memory and peripheral devices<br />
on the I/O bus, concurrent with computations.<br />
2.1.7 Direct Memory Access<br />
The direct-memory-access (DMA) option allows data transfer<br />
into or out of memory modules without disturbing the contents<br />
of the operational registers. Only the Land W registers<br />
are altered. Access to memory using the DMA facility is<br />
on a IIcycle-steal" basis and requires 2.7 microseconds of<br />
processor ti me per tra nsfer .<br />
2. 1 .8 Mi era-EXEC<br />
The Micro-EXEC option is a unique hardware technique for<br />
microstep sequencing of the computer. This option provides<br />
hardware logic in which all computer control signals are<br />
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