Patent GB-1192371-A (GB)
Title: Improvements in or relating to Data Processing Devices
Inventor: THREADGOLD RONALD
IPC: G06F9/22
Filed: 1966-06-02
Abstract: 1,192,371. Data processing device; micro-programme control. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. 19 May, 1967 [2 June, 1966], No. 24595/66. Heading G4A. A micro programme controlled data processing device has control arrangements including multi-section store for controlling the processing of operations involving single cycles, double cycles and iterative cycles. As shown (Fig. 1), a micro-programme controlled stored-programme data processing device comprises a main storage unit MS including a magnetic core matrix store MX storing 24-bit instruction and data words, a control unit CU including a micro-programme store ÁPS (e.g. a diode matrix read-only store) which is arranged in six sections (Fig. 2, not shown) and a clock control CC, a processor unit PROC including a parallel adder AC, a fast-access store FAS consisting of a plurality of registers and an input/output unit I/OU for passing data to and from peripheral units (not shown). All the above units are connected by a common 28-bit parallel highway AH by gates which are selectively opened by signals generated by the control unit CU. Data from registers may be OR-ed together simply by connecting them to the highway AH simultaneously. The device operates in a synchronous mode under the control of clock control CC (Fig. 4, not shown) which generates eight control pulses AT1-8 (Fig. 5, not shown) per instruction cycle. The timing is such that an instruction may be accessed from store MX and an operand defined thereby retrieved and operated on in a single instruction cycle period. The cycle of 8 slots may be shortened. The instruction format is shown in Fig. 1c. The function portion of an instruction from store MX is used by control logic CL to define the least significant six bits of an address in micro-programme store ÁPS. Control logic CL supplies the most significant bits which depend on the type of instruction and the number of instruction cycles required to complete the instruction and determine which section of the store ÁPS is accessed. In the case of multicycle instructions, these most significant bits are changed after the initial cycle so that first, second and subsequent cycles are controlled by micro-orders stored in corresponding locations of different sections of the store ÁPS. The final cycle may be controlled by a micro-order stored in a location adjacent to the previous cycle or cycles. In the multiply instruction, which is described in some detail, two digits of the multiplier are examined at a time and multiples of the multiplicand (0X 1X, 2X or 3X) are added into the partial product from registers storing these multiples followed by shift at each stage. The final partial product occupies two registers (RL and RX). Other instructions which are described include autonomous data transfer, register interchange, increment modifier and if not equal to 0 go to label, skip if, and go to (relative label). Other features described include: priority interrupt (Section 6(b)(i), indirect addressing (6(a)) and masking (7(c)) during comparisons involved in conditional operations (e.g. skip if).