doepfer
System A - 100
Sequencer Controller
A-154
3
2. Basic principles
The current step position of the A-155 is determined
by the current
address
of the sequence. The address
reaches from 1 to 8 as the A-155 has eight steps
available. Internally the address is formed by three
digital address signals A0, A1 and A2 having the
valencies 1 (A0), 2 (A1) resp. 4 (A2). The connection
between step position and the digital values for A0, A1
and A2 is as follows:
The "old" control unit of the A-155 simply generates
the address signals A0, A1 and A2 so that the steps
1-8 are selected one after another. If the A-154 is
used to drive the A-155 the old control unit (i.e. the
section with Start/Stop/Step/Reset buttons and input
sockets) is no longer active and the A-154 calculates
the address signals A0, A1 and A2 in a more sophisti-
cated way. The type of address succession depends
upon the selected mode (forward, backward, pendu-
lum, random, CV addressed, loop/one shot).
In serial mode (i.e. if the A-154 is used to drive two
serial running A-155) another address signal A3 with
valency 8 is generated. This signal is used to distin-
guish between the first and second A-155 by means
of voltage controlled switches.
In addition the A-154 even generates clock signal with
both voltage controlled rate and pulsewidth.
If the A-154 is used to control the A-155 the previous
connection between the "old" control unit and the
analog resp. trigger/gate rows of the A-155 has to be
disconnected and the rows have to be connected to
the corresponding signals of the A-154. In the appen-
dix this procedure is described in detail. The combina-
tion of A-154 and A-155 does not work before this
procedure is carried out. It is not sufficient simply to
assemble the A-154 into the A-100 frame !
Step
position
A0
A1
A2
1
low / 0
low / 0
low / 0
2
high / 1
low / 0
low / 0
3
low / 0
high / 1
low / 0
4
high / 1
high / 1
low / 0
5
low / 0
low / 0
high / 1
6
high / 1
low / 0
high / 1
7
low / 0
high / 1
high / 1
8
high / 1
high / 1
high / 1