Table of Contents
Advertisement
9100A-017
vector period is 167 ns. Vector 1 sets the address and control
data. Vector 2 is driven out 167 ns later. IOW is set low so that,
on the next clock cycle, the E clock will be set high. To ensure
that the E clock remains high for the required time, vector 3 and
4 are driven. Vector 5 adds the data to the data bus to meet the
165 ns setup time to the falling edge of the E clock. Finally,
vector 6 sets IOW high, resetting E low, thereby latching the
data. (In this example, all of the timing requirements have been
met for the write cycle except for the 10 ns hold time on R/W
and CS; these cannot be met since the removal of IOW is
required to force the E clock to return low. However, the card
and bus cycle function properly.)
GROUPS [40-21][20-13][1][2][3][4][5)[7][8][6][12-9]
DISPLAY HEX,HEX,BIN
!
A19 -- AO
!
!
!
!
!
! START OF WRITE CYCLE write $3D5, data $55
1 $003D5
2 $003D5
3 $003D5
4 $003D5
5 $003D5
6 $003D5
STOP
(Note that the grouping of vectors in the file with a few
comments can be self-documenting. By using the appropriate
mixture of hexadecimal and binary vector entry, a very readable
file results. Also, the GROUPS statement in the vector file
allows flexibility in mapping the module pins to the fixture
while maintaining a readable vector file.)
The following CRT Controller Read Cycle Vector File contains
the vectors necessary to perform the read cycle. The read cycle
is almost identical to the write cycle except for a few points.
IOR is used in place of the IOW line. The data lines are not
driven since the CGA Card provides the bus data. After vector 5,
the CAPTURE statement is entered to clock the input section. At
the time the actual clocking occurs, the E clock will have been
7-8
CRT Controller Write Cycle Vector File
D7-DO
$XX
$XX
$XX
$XX
$55
$55
I
I
M
M
A
R
I
O
O
E
E
E
E
O
R
W
M
M
N
S
R
-
-
W
R
E
D
-
-
T
Y
1
1
1
1
0
0
X
1
0
1
1
0
0
X
1
0
1
1
0
0
X
1
0
1
1
0
0
X
1
0
1
1
0
0
X
1
1
1
1
0
0
X
I
UNUSED
O
C
L
K
X
XXXX
X
XXXX
X
XXXX
X
XXXX
X
XXXX
X
XXXX
Advertisement
Table of Contents
