┌─────────────────────────────────────────────────────╖
     │ 3. FIELD OF MCU (microprogramming control unit).    ║
     ╘═════════════════════════════════════════════════════╝

 The microprogramming control unit (MCU) is built with use of 
 chip KM1804BY4, which is intended to control the sequence samples 
 of the microinstructions  from the microinstructions  (MIM).
 The microcircuit  provides  shaping  12-bit address of the 
 microinstruction  i.e.  volume  MIM can  form 4096  words.  Each 
 microinstruction, keeping in  MIM  contains  the field,  that are 
 controlling KM1804BY4 chip and framing equipment. 

 Includes:
           Chip BY4:
           BY4_MI² - Microinstruction;
           CCE     - Permit of the condition analysis;
           COM     - Inversion of condition entry;
           CI      - Forming the address of the next microinstruction;
           RLD     - Unconditional loading of the address / counter register;

           MS      - Multiplexer that selects the signal condition.


 ┌───────────╖
 │BY4_MI².4-0║  MICROINSTRUCTION OF THE KM1804BY4 CHIP.
 ╘═══════════╝   ──────────────────────────────────────┘
 Purpose.
           The microinstructions field of BY4 chip (unit of micropro-
           gramming control ). Correspondence  to  between opcode and 
           executed function was provided in table. 
 ┌────┬─────────────────┬───────────────────────────────────────────────┐
 │ MI │                 │                                               │
 │3210│   Mnemonics     │      microinstruction executed in BY4         │
 ├────┼─────────────────┼───────────────────────────────────────────────┤
 │0000│ JZ;             │transition to zero address                     │
 │0001│ CJS Cond,Addr;  │conditional transition in subprogram by adress │
 │    │                 │from the microcommand register                 │
 │0010│ JMAP Addr;      │transition to address by decoder of commands   │
 │0011│ CJP Cond,Addr;  │conditional transition to address from register│
 │    │                 │of the microinstructions                       │
 │0100│ PUSH Cond,Val;  │record in stack and conditional record in      │
 │    │                 │register of adress                             │
 │0101│ JSRP Cond,Addr; │transition to one of two subroutines: by adress│
 │    │                 │or from RA, or from register of the microinstr.│
 │0110│ CJV Cond;       │condit. trans. to address from external source │
 │0111│ JRP Cond,Addr;  │transit. to addr., conditionally chosen or from│
 │    │                 │ RÇ,  or from register of microinstruction     │
 │1000│ RFCT;           │repetition of the cycle if counter RA <> 0     │
 │1001│ RPCT Addr;      │repetition of the address from register of the │
 │    │                 │microinstructions if counter RA <> 0           │
 │1010│ CRTN Cond;      │conditional return from subprogram       │
 │1011│ CJPP Cond,Addr; │conditional transition to address from register│
 │    │                 │of microinstruction and reading from stack     │
 │1100│ LDCT Val;       │record in RA                                   │
 │1101│ LOOP Cond;      │conditional cessation of the cycle             │
 │1110│ CONT;           │continuation of the work                       │
 │1111│ TWB Cond,Addr;  │branching on three directions                  │
 └────┴─────────────────┴───────────────────────────────────────────────┘
 Where Cond    - checked condition;
     Addr, Val - numerical values of the transition address and loading RA.
 The note.
          Values are  entered in  binary code, that indicated by the  
          symbol '²'on the top of field identifier  (IM²).
          When entered a new command the code 1110 became assigned.           


 ┌────────╖
 │  CCE   ║  PERMIT AN ANALYSIS OF THE CONDITION SIGNAL.
 ╘════════╝   ──────────────────────────────────────────┘
 Purpose.
           Permit an analysis of the condition signal.
 Level  :  0 - Active  (analisys permit)
           1 - Passive (analisys prohibited).
 The note.
           Values are entered in binary code.
           When entering the new command the analisys of command are prohibited.


 ┌─────────╖
 │  COM    ║  INVERSION OF INPUT CONDITION.
 ╘═════════╝   ────────────────────────────┘
 Purpose.
           Inversion of input condition. Provides inversion 
           of analysed in UMC signal.
 Level  :  1 - Active  (inversion permit)
           0 - Passive (inversion prohibited).
 The note.
           Values are entered in binary code.
           When entering a new command the input condition are not inverted.

 ┌─────────╖
 │   CI    ║  SIGNAL FOR CALCULATION OF THE NEXT MC ADDRESS.
 ╘═════════╝   ─────────────────────────────────────────────┘
 Purpose.
           Forming  the  address  of  the  next  microinstruction. In each 
           tact  to  output  address  is   added  values  of  the   signal 
           at the input of CI, and that provides the automatic calculation 
           of the address of the next microinstruction.            
 Level  :  1 - Active  (address of the following microinstruction 
               is formed);
           0 - Passive (address of the next microinstruction 
               is not formed).
 The note.
            Values are entered in binary code.
            When entering the new command incriment of the register is given.


 ┌─────────╖
 │   RLD   ║  UNCONDITIONAL LOADING OF A/CR.
 ╘═════════╝   ──────────────────────────────┘
 Purpose.
           Unconditional loading of the address/counter register 
           with values from bus of branching address. 
 Level  :  0 - Active  (loading  permit)
           1 - Passive (loading  prohibited).
 The note.
           Values are entered in binary code.
           When entering the new command save of the adress register is prohibited.


 ┌─────────╖
 │   MS    ║  MULTIPLEXER OF THE CONDITIONS.
 ╘═════════╝   ─────────────────────────────┘
 Purpose.
           The signal conditionselect multiplexer. This signal 
           (from 0 to 7) provide presenting on entering of the logical 
           condition one  of  8  signals, which adjustment is executed 
           at switching of the connection. 
                ┌────────┬────────┐
                │controll│ output │
                │        │   MS   │
                ├────────┼────────┤
                │   000  │  Z     │
                │001..110│ L1..L6 │
                │   111  │  NZ    │
                └────────┴────────┘
 The note.
           To entry, from 1 to 6, is possible to connect any signal, 
           provided in adjustment.
           When entering a  new  command  the  code from entry MS is 
           given as 000.