Sensoray 421 - Manual (Page 11)

Sensoray Model 421 Instruction Manual Page 9
Relay Interface
Register
I/O Channel
Local
Data
Bus
One of 48 Digital I/O Channels
O.C.
RELAYx Ports
The 48 digital I/O channels are organized as two
banks of three byte-wide ports. Each port accesses
eight relay channels simultaneously, and each bank
of three ports addresses 24 relay channels.
RELAY0 ( 8):
RELAY1 ( 9):
RELAY2 (10):
RELAY3 ( 16):
RELAY4 ( 17):
RELAY5 (18):
Each RELAYx port may be read from or written to
at any time. Reading from a RELAYx port returns
the physical state of the channels associated with
that port. Writing to a RELAYx port programs the
associated relay channel output registers.
Note: the value read from a relay channel may not
be the same as the value stored in that channels
output register. Specifically, the values will differ
if an output register is programmed to 0 and an
external sink pulls the corresponding channel down
to 0V.
Configuring I/O Type
Each channel may be independently configured as
either an input or output via software. To configure
a channel as an input, set the associated channel
register to 0.
R
7
R
6
R
5
R
4
R
3
R
2
R
1
R
0
R
15
R
14
R
13
R
12
R
11
R
10
R
9
R
8
R
23
R
22
R
21
R
20
R
19
R
18
R
17
R
16
R
7
R
6
R
5
R
4
R
3
R
2
R
1
R
0
R
15
R
14
R
13
R
12
R
11
R
10
R
9
R
8
R
23
R
22
R
21
R
20
R
19
R
18
R
17
R
16
Connections
All electrical connections are made through 50-pin
connectors P5 and P6. On each of these connectors,
one pin is assigned to each active-low I/O channel.
All even pins are connected to ISAbus five volt
return. In addition, pin 49 may be used to supply
limited five volt power (<100mA) to an external
relay rack.
The 421 provides 48 high-current digital I/O
channels for direct interface to industry standard
relay racks.
As shown in the diagram to the right, digital I/O
channels are physically structured as open-
collector buffers (with pullup resistors) looped
back to the local data bus by tri-state buffers.
Channel data is active-high on the local bus side,
and active-low on the I/O channel side.
Connectors P5 and P6: Digital I/O
Pin Name Function
1 CH23 I/O Channel 23
3 CH22 I/O Channel 22
5 CH21 I/O Channel 21
7 CH20 I/O Channel 20
9 CH19 I/O Channel 19
11 CH18 I/O Channel 18
13 CH17 I/O Channel 17
15 CH16 I/O Channel 16
17 CH15 I/O Channel 15
19 CH14 I/O Channel 14
21 CH13 I/O Channel 13
23 CH12 I/O Channel 12
25 CH11 I/O Channel 11
27 CH10 I/O Channel 10
29 CH9 I/O Channel 9
31 CH8 I/O Channel 8
33 CH7 I/O Channel 7
35 CH6 I/O Channel 6
37 CH5 I/O Channel 5
39 CH4 I/O Channel 4
41 CH3 I/O Channel 3
43 CH2 I/O Channel 2
45 CH1 I/O Channel 1
47 CH0 I/O Channel 0
49 +5V +5V power
Even GND 5V return