Principles of Operation
6-5
On the mother board, U131, U129, U128, U127, and U130
form an 8-bit parallel-in, serial out data converter. When the
microprocessor executes a write to the address decoded for
U131 (a 74HCT165 shift register), the data bus contents are
loaded into U131, and all ones are loaded into U129
(74HCT165) causing its output OH to go high.
At the end of the write cycle, the SELECT RELAYDATA
decode line goes high, causing the output of the U128
(74HCT08) AND gate to go high. This signal (ACTIVE)
gates the microprocessor E clock through a U127
(74HCT00) NAND, which is buffered by U137 and sent to
the cards as the CLK signal. Clock cycles are counted by the
U129 shift register. After 8 cycles, OH of U129 returns low,
disabling further CLK pulses.
The U130 (74HCT74) flip-flop and another U127 NAND
gate are used to create an inverted version of CLK, which
does not start until after one cycle of CLK. This signal is
used to shift data out of the U131 RELAYDATA shift
register.
Figure 6-4
Matrix card interface simplified schematic
ACTIVE
E
HCT00
U127
U137
U127
U128
HCT08
HCT74
CLR
Q
D
+5V
U137
RELAYDATA
HCT244
HCT00
H
F
E
G
D
C
B
A
HCT165
OH
I N
SH/LD
U129
SELECT RELAYDATA
H
F
E
G
D
C
B
A
HCT165
OH
I N
SH/LD
U131
N.C.
+5V
D7
D0
68B09
Data
Bus
O3
O2
16P8A
U130
U102
HCT164
H
F
E
G
D
C
B
A
IN A
IN B
HCT244
U116
ID 0
ID 1
ID 2
ID 3
ID 4
ID 5
ID 6
ID 7
PA 0
PA 1
PA 2
PA 3
PA 4
PA 5
PA 6
PA 7
VIA
U103
HCT244
+5V
IDDATA
CLK
PB3
PB2
U137
U137
U137
HCT244
CLRADDR
NEXTADDR
8D
7D
6D
5D
4D
3D
2D
1D
D7
D0
68B09
Data
Bus
8Q
7Q
6Q
5Q
4Q
3Q
2Q
1Q
STROBE
CARD 6
CARD 5
CARD 4
CARD 3
CARD 2
CARD 1
HCT374
U119
SELECT CARDSEL
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
Summary of Contents for 708A
Page 135: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 136: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 137: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 138: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 139: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 145: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 146: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 147: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 148: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 149: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 150: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...