This page describes the additional instructions of the CDP1804 which is the successor of the CDP1802.
This info is also available online on the Emma 02 site.
| xx | 8 bit value |
| xxxx | 16 bit value |
| RN | Register number N (N = 0 to F), RN can also be represented as N in all commands |
| RX | Stack or data pointer register |
| RP | Program counter register |
| RN.0, RX.0 or RP.0 | Lower order byte or RN, RX or RP |
| RN.1, RX.1 or RP.1 | Higher order byte or RN, RX or RP |
| M(RN)->D; RN+1->RN | This notation means: The memory byte pointed to by RN is loaded into D, and RN is incremented by 1. |
| INSTRUCTION | MNEMONIC | OP CODE | OPERATION |
| MEMORY REFERENCE | |||
| REGISTER LOAD IMMEDIATE | RLDI RN,xxxx | 68CN | M(RP)->RN.1; M(RP+1)->R(N).0; RP+2-RP |
| REGISTER LOAD VIA X AND ADVANCE | RLXA RN | 686N | M(RX)->RN.1; M(RX+1)->RN.0; RX+2->RX |
| REGISTER STORE VIA X AND DECREMENT | RSXD RN | 68AN | RN.0->M(RX); RN.1->M(RX-1); RX-2->RX |
| REGISTER OPERATIONS | |||
| REGISTER N TO REGISTER X COPY | RNX RN | 68BN | RN->RX |
| BRANCH INSTRUCTIONS-SHORT BRANCH | |||
| SHORT BRANCH ON COUNTER INTERRUPT | BCI xx | 683E | IF CI=1, M(RP)->RP.0; O->CI ELSE RP+1->RP |
| SHORT BRANCH ON EXTERNAL INTERRUPT | BXI xx | 683F | IF XI=l, M(RP)->RP.0 ELSE RP+1->RP |
| COUNTER INSTRUCTIONS | |||
| LOAD COUNTER | LDC | 6806 | D->COUNTER |
| GET COUNTER | GEC | 6808 | COUNTER->D |
| STOP COUNTER | STPC | 6800 | 0->COUNTER CLOCK |
| DECREMENT COUNTER | DTC | 6801 | COUNTER-1->COUNTER |
| SET TIMER MODE AND START | STM | 6807 | TPA÷32->COUNTER CLOCK |
| SET COUNTER MODE 1 AND START | SCM1 | 6805 | EF1->COUNTER CLOCK |
| SET COUNTER MODE 2 AND START | SCM2 | 6803 | EF2->COUNTER CLOCK |
| SET PULSE WIDTH MODE 1, START | SPM1 | 6804 | TPA*EF1->COUNTER CLOCK; EF1 _/¯ STOPS COUNT |
| SET PULSE WIDTH MODE 2, START | SPM2 | 6802 | TPA*EF2->COUNTER CLOCK; EF2 _/¯ STOPS COUNT |
| ENABLE TOGGLE Q | ETQ | 6809 | IF COUNTER=01 • NEXT COUNTER CLOCK _/¯; !Q->Q |
| INTERRUPT CONTROL | |||
| EXTERNAL INTERRUPT ENABLE | XIE | 680A | 1->XIE |
| EXTERNAL INTERRUPT DISABLE | XID | 680B | 0->XIE |
| COUNTER INTERRUPT ENABLE | CIE | 680C | 1->CIE |
| COUNTER INTERRUPT DISABLE | CID | 680D | 0->CIE |
| CALL AND RETURN | |||
| STANDARD CALL | SCAL R1,xxxx | 688N | RN.0->M(RX); RN.1->M(RX-1); RX-2->RX; RP->RN; M(RN)->RP.1; M(RN+1)->RP.0; RN+2->RN |
| STANDARD RETURN | SRET RN | 689N | RN->RP; M(RX+1)->RN.1; M(RX+2)->RN.0; RX+2->RX |