Boy  -  Thanks for all the information and I have printed it out and
stored it on the zip.
John Keys
----- Original Message -----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Wednesday, June 21, 2000 2:13 PM
Subject: Re: New Finds
  >
 > AM2901APC/7829DP; AM2909PC/7811DP;  AM2907PC/7828DM     Those are 
the
   bigger chips
on the board. 
 OK, the 2901 is a 4 bit ALU slice (4 bit ALU + 16 4 bit registers). 
 The
  2909 is a 4 bit control store address sequencer. The
2907 is a bus
 transceiver/latch chip (and is thus uninteresting!).
 I have found a single-page reference to the Am2900 Evaluation And
 Learning Kit in the back of the 2900 databook. According to that :
 'The system consists of a microprogrammed control unit which controls 
all
  inputs to an AM2901 microprocessor slice. 32 bit
microinstructions are
 entered into a RAM in the control unit using the switch register. Each
 microinstruction contains bits to control the AM2901A's A and B
 addtresses, instruction, carry in and data input. Additional bits in 
the
  microinstruction contol an AM2909 sequencer which
generates the 
addresses
  for the microprogram memory. Once entered,
microinstructions may be
 executed using a single-step clock or using a pulse generator. The LED
 display provides access to nearly every signal path in the system.
 16 'Sequence control' instructions are available, including execute,
 branch conditional, jump-to-subroutine, return, and loop. Because this
 set of sequence instructions is implemented in a PROM, the user can
 devise his own set of operations by programming a new PROM.
 The kit is supplied with 40  IC's, all resistors, capacitors, LEDs and
 switches, the PC board and a manual containing assembly instructions,
 theory, and a set of exercises. The user need only solder the 
components
  in place and attach a 5V power supply (2.0A
rating)'
 From the picture of the unassembled kit, there
appears to be 1 40 pin 
 chip (the 2901), one 28 pin chip (the 2909), a couple of
other 
'special'
  chips (the branch instruction PROM and?), 36 other
chips (all look to 
be
  14 or 16 pin), some toggle switches, some pushbutton
switches and a 
box
  of discretes.
 A couple of things may not be too clear from the above description
 (particularly if you don't know the 2900 series). The 'RAM' mentioned
 above is also called the 'control store' or the 'microprogram memory'.
 It's where you store microcode instructions to control the 2901 
(you'll
  _need_ the data sheet for this!) and the 2909. The
PROM sits between 
the
  microprogram memory and the 2909 and basically decodes
some of the
 microinstruction bits into the 2909 control lines. Which gives you a
 (useful) subset of all the operations the 2909 can perform.
 I hope that's of some help.
  John Keys 
 -tony