thing is to connect the Interface's Transmit Data (TD) signal (pin 2) to the host's Receive data (RD)
signal, the Interface's Receive Data (RD) signal (pin 3) to the host's Transmit Data (TD) signal, and the
Interface's Ground (pin 7) to the host's Ground. The table below lists the signals present on the
Interface's DB-25 connector P2 and their usage for each of the possible RS interface standards.
PIN# SIGNAL NAME DIRECTION RS232 RS423 RS422
2 TD - Transmitted Data From Interface R R R
14 TD* - Inverted TD From Interface U U R
3 RD - Received Data To Interface R R R
16 RD* - Inverted RD To Interface U U R
7 GND - Signal Ground - R R R
6 DSR - Data Set Ready To Interface O O O
11 DSR* - Inverted DSR To Interface U U O
20 DTR - Data Terminal Ready From Interface H H H
18 DTR* - Inverted DTR From Interface U U H
5 CTS - Clear To Send To Interface O O O
13 CTS* - Inverted CTS To Interface U U O
** RTS - Request To Send From Interface H H H
** RTS* - Inverted RTS From Interface U U H
25 +5V - Power-OOO
Usage Symbols: R - Required for this configuration
U - Unused in this configuration
O - Optional, Interface doesn't care*, Host may
H - Host dependent, see Host's requirements
* When the DSR and CTS inputs are left unconnected, they are normally read as "true" levels.
However, in high EMI situations, it is recommended that unused DSR or CTS inputs be connected to
the +5V power and unused DSR* or CTS* inputs be connected to GROUND.
** Due to Line Driver limitations, the Request To Send signal is not present at connector P2. It is
implemented by the Interface's ACIA, and asserted true before each transmission is initiated. If desired,
Data Terminal Ready (which is true whenever the Interface is on) can be replaced with Request to Send
by cutting the trace from U2 pin 11 to U3 pin 7 and adding a jumper from U2 pin 8 to U3 pin 7.
The Interface does not require the complete RS-232 protocol to operate but some hosts do. If you
would like to bypass this regimen on the host the easiest thing to do is connect the Host's DSR to its
DTR and its RTS to its CTS. This is accomplished with 2 jumpers on the host's "D" connector. Check
your host's operating manual for its protocol requirements and the corresponding pin numbers.
2.11 DEFAULT OPERATING MODE
The remaining jumper on P3, "M2", directs the Interface to select between Polled or Non-polled
operation. Mode 2 or polled operation is selected if this jumper is on at reset and causes the Interface
to buffer Tags until a transfer command is received from the host. Mode 1, selected if the jumper is
To Next Page
Loading...