HP Portable PLUS - Modem Interface; Direct-Connect Modem (Dealer-Installed Option); Modem Interface Connector Pin Assignments

Portable PLUS Computer
Functional Description 5·9
5.12 Modem Interface
The computer-to-modem interface is contained in 12-pin connector A2J8 with pin assignment listed in
table 5-3. (The mating 12-pin connector on the optional modem is designated A3J2.)
Table 5·3. Modem Interface Connector Pin Assignments
Pin Number
I Signal Name I
Description
1
2
3, 5, 7,
4
6
8
9
10
12
11
MRESET*
MRING*
GND
MSOUT
MSIN
MCARRIER
VBAT
MODEMON
RCM
Modem reset output (active low).
Ring indicate input from modem (active low).
Logic ground
Data transmit output (Mark = 5.0V).
Data received input (Mark = O.OV) .
Carrier detect input (active high).
. Battery supply voltage (approximately +6.5V) .
Power on enable output to modem (active high).
Return-to-command mode output (active high).
The modem's return-to-command mode is directly controlled by output PA4 on the PPU (A2U17, pin
7) . Modem power and reset (MODEMON and MRESET*) are controlled by PPU outputs PD4 and
PA2 (A2U17, pins 33 and 9). When MODEMON (PD4) goes high, the modem's power supply turns
on; when MODEMON goes low, the modem power turns off. When the modem is off, MRESET* can
be either high or low: MRESET* (PA2) should be taken low at the same time as MODEMON (PD4) to
conserve battery power.
Note: Since the modem can be off when the computer is on, the modem and computer power
supplies are isolated from each other.
5.13 Direct-Connect Modem (Dealer-Installed Option)
The modem PCA (HP 82983A) is a Bell 212A-compatible intelligent modem with auto-answer and
auto-dial capabilities using either DTMF (touch-tone) or pulse dialing. It can transmit 1200 bps Di-bit
Phase Shift Keyed (DPSK) and Bell 103J (0 thru 300 bps) Frequency Shift Keyed (FSK) messages.
Commands and appropriate responses for the most common modem functions are built-in. These
commands are a superset of the Hayes Smartmodem command set. The Portable PLUS can run many
of the software packages which use the Smartrnodem standard, thus taking full advantage of the
modem's capabilities.
Connections are made to the motherboard PCA via 12-pin connector A3J2 on the modem PCA (A2J8
on the motherboard PCA). (Refer to table 5-3 for connector pin assignments.)