diff --git a/readme.md b/readme.md index fd05f88..0b94a2d 100644 --- a/readme.md +++ b/readme.md @@ -1,11 +1,14 @@ # Cardiograph computers -The Cardiographs are a pair of imaginary computers. -The "Cardiograph Mark I" is an educational model of a mainframe machine. -The "MicroCardiograph" is a its miniaturized descendent, a microprocessor trainer. -They use the same instruction set and have very similar CPUs. +The Cardiographs are a pair of imaginary computers: + +- "Cardiograph Mark I" is an educational model of a mainframe machine +- "MicroCardiograph" is a its miniaturized descendent, a microprocessor trainer + +They use the same instruction set and have very similar CPUs. (TODO: is that true?) + The main difference is in their peripheral hardware: -the Mark I is designed for batch processing programs on punched cards, +the Mark I is designed for batch processing and supports punched-card input, while the MicroCardiograph is designed to be used interactively. The Cardiographs were built by an imaginary enterprise, the Electronic Computer Group (ECG). @@ -18,76 +21,96 @@ There is a [simulator](micro/readme-micro.md) for the MicroCardiograph. ### Registers -There are three 8-bit registers: +There are four 8-bit registers: 1. **A**, the accumulator (and the only general-purpose register) 2. **IP**, the instruction pointer (aka program counter) +3. **IOD**, the ID of the current I/O device 3. **Status** #### Status register -The *high byte* holds the ID number of the current **IO** device. (See the section on [IO programming](#io-programming).) +The *high byte* holds the state of the four Sense Switches. (TODO: is this easy enough to do in hardware?) The *low byte* holds four flags: **O**verflow, **N**egative, **Z**ero, and **C**arry. -The flags are accessed by number: +These are all addressed by number:* -| O | N | Z | C | -|---|---|---|---| -| 8 | 4 | 2 | 1 | +| S1 | S2 | S3 | S4 | | O | N | Z | C | +|----|----|----|----|-|----|----|----|----| +| 80 | 40 | 20 | 10 | | 08 | 04 | 02 | 01 | + +* (Because the core instruction set doesn't include bitwise operations) ### Instruction set - Instructions are two bytes long: one byte for the opcode, one for the operand +TODO: revise this based on note dated 2023-09-24 + ```GGMM IIII``` - **G**roup, **M**ode, **I**nstruction -| lo ↓ / hi → | 0 (G0, M0) | 5 (G1, M1) | 6 (G1, M2) | 9 (G2, M1) | A (G2, M2) | -|-------------|------------|------------|------------|------------|------------| -| **0** | END | LDA # | LDA ind | DEV # | DEV ind | -| **1** | NOP | STO # | STO ind | INP # | INP ind | -| **2** | | ADD # | ADD ind | OUT # | OUT ind | -| **3** | | SUB # | SUB ind | FED | FED | -| **4** | | JMP # | JMP ind | | | -| **5** | | JEQ # | JEQ ind | | | -| **6** | | JFL # | JFL ind | | | -| **7** | | FTG # | FTG ind | | | -| | | | | | | -| **8** | | MUL # | MUL ind | | | -| **9** | | DIV # | DIV ind | | | -| **A** | | RRL # | RRL ind | | | -| **B** | | RRR # | RRR ind | | | -| **C** | | ARL # | ARL ind | | | -| **D** | | ARR # | ARR ind | | | -| **E** | | JLT # | JLT ind | | | -| **F** | | JGT # | JGT ind | | | +| lo ↓ / hi → | 0 (G0, M0) | 5 (G1, M1) | 6 (G1, M2) | 9 (G2, M1) | A (G2, M2) | F (G3, M3) | +|-------------|------------|------------|------------|------------|------------|------------| +| **0** | END | LDA # | LDA ind | DEV # | DEV ind | | +| **1** | NOP | STO # | STO ind | INP # | INP ind | | +| **2** | | ADD # | ADD ind | OUT # | OUT ind | | +| **3** | | SUB # | SUB ind | FED | FED | | +| **4** | | JMP # | JMP ind | | | | +| **5** | | JEQ # | JEQ ind | | | | +| **6** | | JFL # | JFL ind | | | | +| **7** | | FTG # | FTG ind | | | | +| | | | | | | | +| **8** | | MUL # | MUL ind | | | RSL A | +| **9** | | DIV # | DIV ind | | | RSR A | +| **A** | | JLT # | JLT # | | | ASL A | +| **B** | | JGT # | JGT # | | | ASR A | +| **C** | | NOT # | NOT # | | | | +| **D** | | AND # | AND # | | | | +| **E** | | OR # | OR # | | | | +| **F** | | XOR # | XOR # | | | | -- RRL/RRR: Ring Rotate -- JLT: Jump Less Than +TODO: assess JMPs vs. HOPs -- DEV: IO device select +- RSL/RSR: Ring Shift Left/Right +- JLT/JGT: Jump Less/Greater Than +- DEV: select IO device - FED: "feed" - line feed / end of card -TODO: assess JMPs vs. HOPs +TODO: format/document better: + +1. core computational operations: low nibbles of 0x, 5x, 6x +2. arithmetic extension (optional): MUL, DIV +3. IO extension (optional): 9x, Ax +4. bitwise arithmetic extension (optional): NOT, AND, OR, XOR and RSL, RSR, ASL, ASR +5. control flow extension (optional): JLT, JGT + +- The mainframe system implements at least 1, 2, and 3 +- The microprocessor trainer implements 1 +- (see note dated 2023-09-24) ### Connections (pinout) TBC -| number | name | in/out? | description | -|---------|-----------|---------|---------------| -| 1 | RST | in | *reset* | -| 2 | VCC | in | *power* | -| 3 | GND | in | *ground* | -| 4 | CLK | in | *clock* | -| 5 - 13 | A0 - A7 | out | *address bus* | -| 15 - 23 | D0 - D7 | out | *data bus* | -| 24 | ABE | out | *address bus enable*:
low when the CPU is using the address bus | -| 25 | DBE | out | *data bus enable*:
low when the CPU is using the data bus | -| 26 | WAIT | in | *wait* — when pulled low,
the current operation is completed
and then execution pauses | +| name | in/out? | description | +|-----------|---------|---------------| +| RST | in | *reset* | +| VCC | in | *power* | +| GND | in | *ground* | +| CLK | in | *clock* | +| A0 - A7 | out | *address bus* | +| D0 - D7 | out | *data bus* | +| ABE | out | *address bus enable*:
low when the CPU is using the address bus | +| DBE | out | *data bus enable*:
low when the CPU is using the data bus | +| WAIT | in | *wait* — when pulled low,
the current operation is completed
and then execution pauses | +| /RD | out | TODO | +| /WR | out | | +| M/IO | out | | + ### Start-up @@ -106,15 +129,13 @@ The components of a Mark I are: - an ECG 101 Central Processing Unit - an ECG 102 Core Memory Unit -- an ECG 103 Card Reader -- an ECG 104 Card Punch -- an ECG 105 Line Printer -- an ECG 106 Matrix Display - -Additionally, an *ECG 100 Keypunch* is used for the initial preparation of cards or tape. +- an ECG 103 Print-Key-Punch +- an ECG 104 Matrix Display ### Console +TBC TBC TBC + The console is equipped with: - Power switch @@ -126,12 +147,13 @@ The console is equipped with: - Memory Read Next button - Memory Write button - Memory Write Next button -- 16 Sense switches (TBC) +- 4 Sense Switches + - 8 Accumulator lights - 8 Address lights - 8 Data lights -- 8 Instruction Pointer lights (TBC) -- 4 Status Register lights +- 8 Instruction Pointer lights (review IP size?) +- 8 Status Register lights ## IO programming @@ -140,23 +162,31 @@ Only one input or output device can be accessed at a time. ### Reading data 1. Use `DEV xx` to select input device _xx_ -2. Use `INP yy` to read one card into memory, beginning at address _yy_ +2. Use `INP yy` to read one byte into memory at address _yy_ + +TODO: find a way to allow the input device to refuse to provide input ### Writing data 1. Use `DEV xx` to select output device _xx_ -2. Use `OUT yy` to write one byte -3. Use `FED xx` to signal the end of a card, or the end of a line on the printer or display +2. Use `OUT yy` to write one byte from memory at address _yy_ +3. Use `FED xx` to... + - card punch: load a new card + - printer: begin a new line (CR, LF) + - display: begin a new line ### Punched card format -- Cards are punched in EBCDIC -- EBCDIC data is translated into binary by the card reader/punch +FIXME: +- ~~Cards are punched in EBCDIC~~ +- ~~EBCDIC data is translated into binary by the card reader/punch~~ - Only columns 1-64 are used (for a maximum of 64 bytes of data per card) ### Printer format -The printer can print up to 64 characters per line. +- The printer format is the same as the card format +- One line of printing is equivalent to one card +- The printer can print up to 64 characters per line ### Matrix display format @@ -168,11 +198,31 @@ The printer can print up to 64 characters per line. ### Device numbers -1. Input - Card Reader -2. Output - Card Punch -3. Output - Line Printer -4. Output - Matrix Display +1. card reader / typewriter +2. card punch / line printer +3. display +### Print-Key-Punch configurations + +A dial allows you to select which input device to connect to the CPU: + +1. none +2. card reader +3. keyboard + +A similar dial selects the output device to connect: + +1. none +2. card punch +3. printer + +Thus, this all-in-one device allows the following configurations: + +| | printer | card punch | none | +|-----------------|----------------------|------------------|--------------------------| +| **keyboard** | ***teletypewriter*** | ***auto punch*** | ***keypunch (offline)*** | +| **card reader** | (keys + print) | card duplicator | (card reader) | +| **none** | line printer | (auto punch) | (scrap metal) | ## MicroCardiograph (microprocessor trainer)