3 stable releases
2.0.1 | Feb 25, 2024 |
---|---|
1.0.0 | Feb 11, 2024 |
#131 in Emulators
32 downloads per month
Used in z80emu
605KB
12K
SLoC
RAL 1243
RAL 1243
is a fictional computer brought into its virtual existence to provide an example on how to implement emulators based on z80emu Z80 CPU emulator.
The computer has no graphics or a keyboard interface but instead communicates with the user via the PIO onboard chipset.
Library
The RAL 1243
computer is a library. Ready for embedded.
Usage
An example using this library can be found in z80emu/examples, called terminal
.
Memory
The memory map of RAL 1243
:
0x0000
-0x1FFF
occupies theROM
kernel.0x2000
-0x3FFF
occupies a swappableEX-ROM
cardridges with user programs or a kernel only accessibleRAM
page.0x4000
-RAMTOP
Random Access Memory available for user programs.
Traps:
If the Program Counter is between 0x0000
and 0x1FFF
(inclusive) the RAM
page is being swapped into memory page 0x2000
-0x3FFF
. Otherwise, the currently swapped cartridge ROM
is available on this memory page.
I/O
I/O is handled by the daisy-chained devices on the system Bus
where the following peripherals are present:
Memory Controller
IN (124)
- Reads the currently swapped in cartridge number.OUT (124)
- Selects one of 256 swappable cartridges to be mapped at the memory page0x2000
-0x3FFF
. If the cartridge doesn't exist a0xFF
byte-filled page appears instead.
PIO Z8420
A single PIO Z8420
chip controls the terminal input connected to its Channel A
and the output from its Channel B
.
NOTE: The implementation of the PIO chip emulates only input
and output
channel modes. The bi-directional and control modes are not currently supported.
IN (8)
- Reads a character from the terminal viaChannel
A
.OUT (9)
-PIO
Channel
A
control.OUT (10)
- Outputs a character to the terminal viaChannel
B
.OUT (11)
-PIO
Channel
B
control.
PIO
chip triggers interrupts signaling the terminal input and output data availability.
CTC Z8430
A single CTC Z8430
chip controls 4 timers/counters.
-
CLK/TRG
lines of channels0
and2
are connected to a (CPU clock independent) 100µs pulse (10 kHz) clock. -
the
ZT/CO
line ofChannel
0
is connected to theCLK/TRG
line ofChannel
1
. -
the
ZT/CO
line ofChannel
1
is currently not connected to anything. -
the
ZT/CO
line ofChannel
2
is connected to theCLK/TRG
line ofChannel
3
. -
IN (4)
-CTC
Channel
0
current counter value. -
OUT (4)
-CTC
Channel
0
control. -
IN (5)
-CTC
Channel
1
current counter value. -
OUT (5)
-CTC
Channel
1
control. -
IN (6)
-CTC
Channel
2
current counter value. -
OUT (6)
-CTC
Channel
2
control. -
IN (7)
-CTC
Channel
3
current counter value. -
OUT (7)
-CTC
Channel
3
control.
The CTC
chip may trigger interrupts on a countdown to 0
.
Interrupts
IM 2
interrupt mode must be always on.
System
The RAM
memory area mapped between 0x2000
and 0x3FFF
is for exclusive use by the ROM kernel only.
The machine stack occupies the last bytes of RAM
memory. SP
is initiated to the last address of available RAM
+ 1 after boot. System refuse to start if no user RAM
memory is detected.
RST 00h
- A soft system reset.RST 08h
- Fetches the input character into Accumulator signaling a new character withZF=0
. TheA
register is being modified only on new input. TheHL'
registers are being modified. When called withCF=1
waits until the next character is available, always succeeds. When called withCF=0
returns immediately, signalling a possible failure withZF=1
.RST 10h
- Outputs a single character given in Accumulator signalling the success withZF=1
. TheHL'
registers are being modified. When called withCF=0
waits until the character could be buffered, always succeeds. When called withCF=1
returns immediately, signalling a possible failure withZF=0
.RST 18h
- Forwards a call to an address inIX
.RST 20h
- Forwards a call to an address inIY
.RST 28h
- Forwards to one of the syslib functions identified as an 8-bit function vector in the Accumulator. ModifiesA
andHL'
. Functions may alter more registers. For a list of system library routines consult theROM
kernel source rom/ral1243_rom.rb.RST 30h
- Forwards a call to an address inHL
.RST 38h
- Back to system menu.NMI
- Back to system menu if running theEX-ROM
code.
Terminal
The terminal forwards any user key input to the RAL 1243
PIO
input device.
Keys wired to control codes sent to PIO
A
:
key name | data |
---|---|
PgUp |
1 |
Home |
2 |
End |
3 |
PgDn |
4 |
Ins |
5 |
Backspace |
8 |
Tab |
9 |
Up |
17 |
Left |
18 |
Down |
19 |
Right |
20 |
Esc |
27 |
Del |
127 |
Any ASCII printable character is forwarded as such.
Data from a PIO
output (Channel
B
) is being forwarded to the console.
Special output control codes interpreted by the terminal:
code | action |
---|---|
8 |
Moves the cursor back left. |
10 |
Moves the cursor to the next line. |
12 |
Clears the terminal. |
13 |
Moves the cursor to the first column. |
16 |
Moves the cursor to an absolute position; followed by a row index, followed by a column index. |
17 |
Moves cursor ↑ up |
18 |
Moves cursor ← left |
19 |
Moves cursor ↓ down |
20 |
Moves cursor → right |
21 |
Changes cursor appearanc; followed by a cursor shape number. |
The cursor shapes:
0
- hidden1
- underscore2
- block
Depending on the terminal capability more shapes may be available.
Dependencies
~185–400KB