External Interface Description - IBM RT Series Hardware Reference Manual

External Interface Description
The adapter provides an asynchronous-like interface.
The pin functions for the 10-pin connector are shown in Figure 9.
PORT
E05 E10
4 9
1 Transmit Data
3 8
A
2
+12 VDC
2
· ·
7
E01 E06
3
+5VDC
4 Not Used
F05 F10
4
9
5 -12 VDC
3 8 B
2
·
·
7
6 Receive Data
F01
F06
7 Not Used
G05
G10
8 Not Used
4
· ·
9
9 Not Used
3
8 C
2 7
10 Ground
G01
· ·
G06
Figure 9.
to-Pin
Interface Signals Connector (viewed from rear of adapter)
The adapter converts the data signals from TTL levels to EIA RS232C voltage levels, and vice
versa. These signals are sampled or generated by the communications control chip and can then be
sensed by the system software to determine the state of the interface or peripheral device. The
drivers and receivers used on the adapter are the inverting type; therefore, a 0 EIA level on the line
is received or transmitted as a 0 TTL level, and a 1 EIA level is received or transmitted as a 1 TTL
level.
Voltage Interchange Information
The signal is considered in the marking condition when the voltage on the interchange circuit,
measured at the interface point, is more negative than -3 V dc with respect to signal ground. The
signal is considered in the spacing condition when the voltage is more positive than + 3 V dc with
respect to signal ground. The region between +3 Vdc and -3 Vdc is the transition region and is
considered an invalid level. The voltage that is more negative than -25 Vdc or more positive than
+ 25 V dc is also considered an invalid level.
10 5080 Peripheral Adapter