1.4
SIM Interface
1 – 7
The mating connector needed is a standard DB–15 receptacle, such as
Amp part # 747909-2 (or equivalent). Clean, well-regulated supply
voltages of
+
5,
±
15 VDC must be provided, following the pin-out
specified in Table 1.1. Ground must be provided on pins 1 and 8,
with chassis ground on pin 9. The
−
STATUS signal may be monitored
on pin 2 for a low-going TTL-compatible output indicating a status
message.
1.4.2.1
Direct interface cabling
If the user intends to directly wire the SIM910 independent of the
SIM900 Mainframe, communication is usually possible by directly
connecting the appropriate interface lines from the SIM910 DB–15
plug to the RS-232 serial port of a personal computer.
1
Connect RXD
from the SIM910 directly to RD on the PC, TXD directly to TD, and
similarly RTS
→
RTS and CTS
→
CTS. In other words, a null-modem
style cable is
not
needed.
To interface directly to the DB–9 male (DTE) RS-232 port typically
found on contemporary personal computers, a cable must be made
with a female DB–15 socket to mate with the SIM910, and a female
DB–9 socket to mate with the PC’s serial port. Separate leads from
the DB–15 need to go to the power supply, making what is sometimes
know as a “hydra” cable. The pin-connections are given in Table 1.2.
DB–15
/
F to SIM910
Name
DB–9
/
F
3
←→
7
RTS
4
←→
8
CTS
10
←→
3
TxD
11
←→
2
RxD
5
Computer Ground
to P
/
S
7
←→
−
15 VDC
14
←→
+
15 VDC
13
←→
+
5 VDC
8,9
←→
Ground (P
/
S return current)
1
←→
Signal Ground (separate wire to Ground)
Table 1.2: SIM910 Direct Interface Cable Pin Assignments
1
Although the serial interface lines on the DB-15 do not satisfy the minimum
voltage levels of the RS-232 standard, they are typically compatible with desktop
personal computers
SIM910
JFET Preamp
