Intel 80386 - Page 283

inter
DRAM PAL DESCRIPTIONS
FUNCTION TABLE
OE CLK REFACKO REFACKI
RFRQ Q7 Q6 Q5 Q4 Q3 Q2 Ql QO
,
;OE
; 1 CLK
;1 1
L C
L C
L C
L C
L C
L C
L C
L C
L C
L C
L C
DESCRIPTION
REFACKO
1 REFACKI
1 1 RFRQ
1 1 1
H X
H
X H H
L L
L
X X
L
X X
L
X X
L
X X
H
H X
H
X H
H
L L
L
X X
L
Q7
1 Q6
1 1 Q5
1 1 1 Q4
1 1 1 1 Q3
1 1 1 1 1 Q2
1 1 1 1 1 1 Ql
1 1 1 1 1 1 1 QO
1 1 1 1 1 1 1 1
L L L L H L H H;
L L L L H L H L;
L L L L H L L
H;
LLLLHLLL;
L L L L L H H H;
H H H H H H H H;
H H H H H H H L;
H H H H H H L
H;
H H H H H H L L;
H H H H H L H
H;
H H H H H L H L;
;
inputs
;outputs
COMMENTS
initial ize(ignore errors
decrement
decrement
decrement
decrement
to 7
reset to 255
decrement, activate RFRQ
decrement, sample REFACKs
decrement, sample REFACKs
on vector)
decrement, both REFACKs: cl ear RFRQ
decrement
Th i s PAL i mpl ements the counter to determi ne when d i stri buted
refresh cycles should be run. This counter counts intervals of 249
clocks which is just under 15 uS at 16 MHz.
The counter counts backwards from 255 to 7. The clock after the
counter reaches 7, the counter
is set to 255 and wi 11 then continues
to decrement. Also when 7 is hit, RFRQ is activated until both
REFACKO and REFACKI are simultaneously sampled low.
Figure C-6. Refresh Interval Counter PAL Equations (Cont'd.)
C-21