Kurzweil K150 - PROGRAMMERS MODEL REV A Hardware Manual page 8

In order to simplify its design and also reduce audible noise, the anti-alias low-pass filter used in the K150FS does not have a
maximally flat passband; instead it gently slopes downward and then cuts off suddenly near the Nyquist frequency. The
effect of this slope is to make the actual output amplitudes of high frequency partials somewhat less than their programmed
amplitudes. The existing K150FS operating software takes this curve into account when it starts notes. User software should
do the same to ensure a "flat" frequency response. The filter response curve is reproduced below to aid in applying the
correction:
Response, dB
0
-2
-4
-6
-8
-10
-12
-14
-16
-18
-20
0
PROGRAM DEVELOPMENT TECHNIQUES
While program development for the K150FS can be successfully done by erasing and reprogramming EPROMs and testing
operation each time a change is made, such a procedure is much like using a batch-processing mainframe computer 15 years
ago. Although Kurzweil programmers use an expensive Hewlett-Packard development system for programming, one can be
almost as productive with a personal computer, a MIDI interface, and the suggestions below.
200
4
MIDI
from
K150
5
The first step in putting together a suitable development system is to get a MIDI interface for the development computer
(called the "host") so that communication with the K150FS is possible. These are available for all of the popular personal
computers. For a campus mainframe offering only RS-232 ports, it is possible to program the MIDI baud rate in the K150FS
to 4800 baud by setting the MC6840 Timer #3 to divide the 1MHz system clock by 13. Then a MIDI to RS-232 level
shifting circuit, such as shown below, can be used for the connection. Either way, you will be using ASCII and perhaps pure
binary code rather than MIDI protocol in communicating between the host and the K150FS for program development
purposes.
Once a communication link is established, the next task is to write a simple program loader and program it into two EPROMs
which are plugged into sockets U55 and U57 of the K150FS. If the loader and the data format is kept simple, it should only
K150FS Programmer's Model
1.0 2.0 3.0
+5V
100
8
2
6N138
6
3
270
1N4148
5
-12V
4.0 5.0 6.0
kHz
From RS-232
Transmit Data
2N2907
To RS-232
Receive Data
2.2K
8
7.0 8.0 9.0
+5V
4
MIDI
220 x 2
to
K150
5
2.2K
2N2222
2.2K
Rev. A 26-APR-88