den@hpfinote.HP.COM (Don Novy) (09/26/90)
Someone requested I post a schematic of this converter. I think the original
question was posted here, but I don't see it any more.
Here is my schematic of a Centronics to HPIB (IEEE-488) converter. This
converter does NOT distinguish between HP-IB devices with different bus
addresses; i.e. ALL HP-IB devices will accept the data. All HP-IB devices MUST
be configured in listen-only mode. Listen-only mode is enabled by either a
switch, or by selecting a reserved bus address (usually 31). Be sure to cycle
the power on all HP-IB devices after changing any switch settings to update the
device configuration.
This converter is also unidirectional, so commands cannot be sent to the HP-IB
devices (commands will be interpreted as data). This is not a problem, since
most Centronics interfaces are also unidirectional.
I make no claims that this circuit is as simple as possible. I present it
because it works. Feel free to distribute it with or without naming me as its
source.
Don Novy
Hewlett-Packard
don_novy@fc.hp.com
Centronics HP-IB (IEEE-488)
INPUT OUTPUT
7414
11 /| 7 ____
BUSY <------------------------O |--------------------------< NRFD
\|
+5
|
+----+
| | T = .28 sec
Any ___ / 5.6K
Si /_\ \
Diode | / 7414 7414
| | |\ |\
GND ---)|--+----+----| O----| O----+
220 uF |/ |/ |
| 7474
+-----------+
+5 1K | _ | 6 ___
| +5 ---/\/---|D S Q|-----> DAV
/ 4.7K | |
\ 74221 | _ |
/ 7414 T = 1 usec | R /\ |
___ 1 | |\ +-----------+ +-----------+
STB >----+----| O----|B _| | |
|/ | Q|-----------+ |
|_ | |
GND --|A | |
|_ | |
+5 ---/\/---|R | |
1K | | |
| C R/C | |
+-----------+ |
| | |
+--)|--+--/\/-- +5 |
120 pF 12K |
|
|
74221 |
T = 10 usec |
+------------+ |
___ 10 |_ | | 8 ____
ACK <----------------|Q B|--------------+--------< NDAC
| |
| _|
| A|-- GND 1K
| _| +--------+---/\/--- +5
| R|---/\/--- +5 | |
| | 1K | | 7474 (unused)
| C R/C | | +----------+
+------------+ | | _ |
| | +---|D S |
+--)|--+--/\/-- +5 | | |
910 pF 16K +---|> _ |
| | R |
| +----------+
| |
+--------+
7414
2 |\ 1
D0 >------------------------| O--------------------------> D0
|/
7414
3 |\ 2
D1 >------------------------| O--------------------------> D1
|/
7414
4 |\ 3
D2 >------------------------| O--------------------------> D2
|/
7414
5 |\ 4
D3 >------------------------| O--------------------------> D3
|/
7414
6 |\ 13
D4 >------------------------| O--------------------------> D4
|/
7414
7 |\ 14
D5 >------------------------| O--------------------------> D5
|/
7414
8 |\ 15
D6 >------------------------| O--------------------------> D6
|/
7414
9 |\ 16
D7 >------------------------| O--------------------------> D7
|/
18, 19, 20
16, 19-30, 34 21, 22, 23, 24
GND <------------------------+-----------------------+----> GND
| |
GND | 12
+----> SHIELD
2.7K 11
+5 ---/\/-----> ATN
2.7K 5
+5 ---/\/-----> EOI
2.7K 9
+5 ---/\/-----> IFC
2.7K 17
+5 ---/\/-----> REN