Specifications

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ANalog Immediate Command
Mode: Command Host: An
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ANALOG is an immediate command that switches Radio Port 1 of your PK-900 into
the ANALOG mode. The Analog mode passes data for communication modes that
require "gray scales" such as FAX. Your PK-900 is automatically placed in the
ANALOG receive condition. Most PK-900 users will not use this mode the way
Packet and Baudot are used. Rather, application programs such as AEA FAX-900
use this mode to process FAX signals allowing gray scale images to be displayed.
In receive, the ANALOG mode enables a zero-crossing audio detector which feeds
this information to the computer via the RS-232 serial port. A computer
program must further process this information for it to be of any use.
In transmit, the PK-900 takes bytes of binary information from the serial port
and converts them to audio frequencies from 900.0 - 2493.75 Hz. This conversion
is done in a linear fashion where $00 corresponds to 900 Hz and $FF corresponds
to 2493.75 Hz. This gives a frequency resolution of 6.25 Hz per step.
This is convenient for FAX transmissions which typically range from 1500 Hz to
2300 Hz. A binary value of $60 received on the serial port will cause the
PK-900 to produce a frequency of 1500 Hz. A binary value of $E0 causes 2300 Hz
to be produced. This allows for fax transmissions with 128 shades of gray.
To use the Analog mode, the program should first set ANSAMPLE then enter the
ANALOG mode. ANALOG initializes in the receive state. The following commands
function in other operating modes and now control the ANALOG mode as well.
R (Receive): Receive. (return to receive)
X (Xmit): Data transmit.
Since binary data is often needed for ANALOG transmission, the CONMODE command
should be set to TRANSparent.
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ANSample "n" Default: 2000
Mode: Analog Host: As
_________________________________ Parameters: __________________________________
"n" - 900 to 65535 decimal specifies a number to be loaded into the 8536
timer chip to control the Analog mode sample rate.
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The value n is sent directly to the 8536 timer chip to control the sample
rate of the ANALOG mode. The number of samples per second is controlled by the
following formula:
Samples/second = 2,000,000 / ANSAMPLE.
The default value of n is 2000, meaning 1000 samples/sec. The lower limit on
ANSAMPLE (900) corresponds to 2,222 Samples/second. Attempting to set ANSAMPLE
to a value lower than 900 (more than 2222 samples per second) produces the
"range" error. This limit may change in the future. Presently, the PK-900
may not be able to keep up with values of ANSAMPLE below 1600.
10/93 A-17