To provide a quick reference summary of the instruction set of the PDP 15.
The instructions are listed by type, the first section consisting of the memory access instructions, the second of operate instructions, which affect the accumulator, the third of operate instructions for the other registers, and a short summary is given of IOT and EAE instructions in the fourth. All references are to pages in the PDP 15 Systems Reference Manual.
Function Mnemonic Meaning Reference 00 CAL JMS 20 7-8 04 DAC Deposit acc in memory 7-5 10 JMS Subroutine jump to address 7-8 14 DZM Deposit zero in address 7-3 20 LAC Load acc from address 7-3 24 XOR Exclusive or of acc and address 7-4 30 ADD One's complement add 7-3 34 TAD Two's complement add 7-3 40 XCT Execute instr at address 7-7 44 ISZ Increment address, skip if zero 7-4 50 AND Logical and of acc and address 7-4 54 SAD Skip if acc different from memory 7-5 60 JMP Jump to address 7-7
Instr in Octal Mnemonic Meaning Reference 740000 NOP DO nothing 7-5 740001 CMA One's complement acc 7-7 740002 CML Complement link 7-6 740004 OAS Or acc and switches 7-6 740010 RAL Rotate acc one left 7-5 740020 RAR Rotate acc one right 7-5 740030 IAC Inc acc by one DO nothing 7-6 740100 SMA Skip if bit 0 of acc is one 7-8 740200 SZA Skip if all of acc is zero 7-8 740400 SNL Skip if link is one 7-9 741000 SKP Skip 7-7 741100 SPA Skip if bit 0 of acc is zero 7-8 741200 SNA Skip if acc is not zero 7-8 741400 SPL Skip if link is zero 7-9 742010 RTL Rotate acc, two left 7-5 742020 RTR Swap acc low and high half 7-6 744000 CLL Set link to zero 7-6 750000 CLA Set acc to zero 7-6 76n LAWn Load acc with this instr 7-7 It is possible to microcode several of these operate instructions together = see 7-11 et al. e.g. 740031 TCA IAC!CMA Two's complement of acc
Instr in Octal Mnemonic Meaning Reference
721000 PAX Put acc in index 7-9
723000 PAL Put acc in limit 7-9
724000 PXA Put index in limit 7-9
730000 PLA Put limit in acc 7-9
731000 PLX Put limit in index 7-9
720 n AAS n Add n to acc, skip if z limit 7-10
725 n AXS n Add n to index, skip if z limit 7-10
737 n AXR n Add n to index 7-10
723 n AAC n Add n to acc 7-10
735000 CLX Clear index 7-10
734000 CLAC Clear acc 7-11
736000 CCLR Clear limit 7-11
It is not possible to microcode these instructions
Instr in Octal Mnemonic Meaning Reference 700314 IORS Read flags to acc 7-13,7-14 700302 CAF Clear all flags 7-13 700002 IOF Interrupts off 7-14 700042 ION Interrupts on 7-14
Instr in Octal Mnemonic Meaning Reference 644000 ABS abs val of acc (1's complement) 8-2 641000 ELCA Clear cc 8-3 6405 n LRSn long right shift n places 8-3 6406 n LISn long left shift n places 8-4 653122 MUL Multipy, unsigned 8-7 640323 DIV Divide, unsigned 8-8 See ch 8 for other EAE's