Computers are machines just like the marionette. They must be told exactly what to do, in specific language. And so we need a language which possesses two seemingly opposite traits: On the one hand, it must be precise in its meaning to the computer, conveying all the information that the computer needs to know to perform the operation. On the other hand, it must be simple and easy-to-use by the programmer.

From chapter "Introduction for Beginners", Leo Brodie, Starting FORTH https://www.forth.com/starting-forth/

Rc/Forth and IDIOT Monitor for RaspiElf (Membership Card)

Mark Abene made FORTH work on the Membership Card.

forth.hex

Modified version of Mike Riley's Rc/Forth, ROM version. Changed to work with my modified version of IDIOT. Loads in at 0500h. You can get it from the COSMAC ELF yahoo group.

idiot_new.hex

New version of IDIOT with SCRT routines, along with TYPE, MSG, READ, and INPUT routines for basic console I/O. Loads in at 0000h. You can get it from the COSMAC ELF yahoo group. For details see http://www.retrotechnology.com/memship/mship_idiot.html

Concatenated this two files as mc-forth.hex and convert it to a binary file:

pi@cosmac:~/elf/forth $ cat idiot_new_qhi.hex forth.hex > mc-forth.hex
pi@cosmac:~/elf/forth $ hex2bin mc-forth.hex 
hex2bin v2.5, Copyright (C) 2017 Jacques Pelletier & contributors

Allocate_Memory_and_Rewind:
Lowest address:   00000000
Highest address:  00001633
Starting address: 00000000
Max Length:       5684

Binary file start = 00000000
Records start     = 00000000
Highest address   = 00001633
Pad Byte          = FF
pi@cosmac:~/elf/forth $ ls -l
insgesamt 40
-rw-r--r-- 1 pi pi 12132 Jan 13 12:36 forth.hex
-rw-r--r-- 1 pi pi  2890 Jan 13 12:36 idiot_new.hex
-rw-r--r-- 1 pi pi  5684 Jan 13 12:41 mc-forth.bin
-rw-r--r-- 1 pi pi 15022 Jan 13 12:36 mc-forth.hex

Now upload and start Rc/Forth (mc-forth.bin):

pi@cosmac:~/elf/forth $ bin2elf -w -r mc-forth.bin
0x1634 bytes written

clear high (8th) bit of input characters

pi@cosmac:~/elf/forth $ stty -F /dev/ttyS0 istrip

and start the terminal emulator (console):

pi@cosmac:~/elf/forth $ microcom -s 600
connected to /dev/ttyS0
Escape character: Ctrl-\
Type the escape character followed by c to get to the menu or q to quit
[CR]
IDIOT/4
*$P500
Rc/Forth 0.1
(c) copyright 2006 by Michael H. Riley
ok 15 5 + .
20 ok BYE

IDIOT/4
*

Rc/Forth and Chuck's Super Monitor for RaspiElf (Membership Card)

Mark Abene made Rc/Forth also work with Chuck's Super Monitor. I prefer this monitor because of its ability to communicate with 9600 baud.

mcsmp_rcforth.hex

Mike Riley's Rc/Forth, modified to work with Chuck Yakym's MCSMP20 firmware. You can get it from the COSMAC ELF yahoo group.

MCSMP20B.bin

Chuck's Super monitor. Loads in at 0000h. You can get it from the Lee A. Hart's website The COSMAC ELF Membership Card .

Create binary file and load it at 0x8000:

pi@cosmac:~/elf/forth $ hex2bin mcsmp_rcforth.hex
hex2bin v2.5, Copyright (C) 2017 Jacques Pelletier & contributors

Allocate_Memory_and_Rewind:
Lowest address:   00008000
Highest address:  000091DB
Starting address: 00008000
Max Length:       4572

Binary file start = 00008000
Records start     = 00008000
Highest address   = 000091DB
Pad Byte          = FF
pi@cosmac:~/elf/forth $ bin2elf -s 8000 mcsmp_rcforth.bin
0x11dc bytes written

Now upload and start the monitor, start the terminal program with 9600 baud:

pi@cosmac:~/elf/forth $ bin2elf -w -r MCSMP20B.bin
0x8000 bytes written
pi@cosmac:~/elf/forth $ microcom -s 9600
connected to /dev/ttyS0
Escape character: Ctrl-\
Type the escape character followed by c to get to the menu or q to quit
[CR]
Membership Card's Serial Monitor Program Ver. 2.0B
Enter "H" for Help.
>R8000
Currently running your program
Rc/Forth 0.1
(c) copyright 2006 by Michael H. Riley
ok 

Night Rider in Rc/Forth

See ChaseLighting for an assembler version (much faster of course).

Here a small test program for the Rc/Forth. It's a simple night rider chase lighting, but it is using the MC LEDs (of course), the switches for setting the pace and the IN button to terminate the program.

Some interactive programming to find out how OUT is working:

ok 1 4 OUT
ok 4 1 OUT
ok 4 2 OUT
ok : LED! 4 SWAP OUT ;
ok 4 LED!

The rest of the program, every word can and should be tested interactively (e.g. 1 LEFT):

: SWITCH@ 4 INP ;
: DELAY 1 SWITCH@ + 0 DO LOOP ;
: LEFT 7 0 DO 2 * DUP LED! DELAY LOOP ;
: RIGHT 7 0 DO 2 / DUP LED! DELAY LOOP ;
: NIGHTRIDER 1 DUP LED! BEGIN LEFT RIGHT EF 8 <> UNTIL DROP ;

Push the IN button to terminate the program.

Mass storage

Forth without mass storage (blocks, screens) is a not complete. A SD-Card interface could be a reasonable solution but this is an overkill for a small Forth system.

EEPROM Serial Communication

Serial Peripheral Interface SPI, MC is the SPI master, the host is the slave. e.g. AT25M02 SPI EEPROM 2Mbit (256 KiB, $3), 25LC1024 (128 KiB, $2), or 25LC512 (64 KiB, $1.50). DIL8 Package. 64/128/256 KiB seems very small for today's standards where storage is quantified in GiB, but I think it's more than enough for a small Forth system. If you want more memory there is 16 MiB serial EEPROM W25Q128J from WINBOND, please note that is a 3.3 V part!

CLK   MC ->- host
MOSI  MC ->- host
MISO  MC -<- host
SS    MC ->- host or other peripherals (optional)

A high-to-low transition on the CS pin is required to start an operation and a low-to-high transition is required to end an operation.

Invalid Opcode: If an invalid opcode is received, no data will be shifted into AT25M02 and the Serial Data Output (SO) pin will remain in a high impedance state until the falling edge of CS is detected again. This will reinitialize the serial communication.

While in Hold mode, the SO pin will be in a high impedance state. In addition, both the SI pin and the SCK pin will be ignored.

25LCxxxx Instruction Set

Name	Format	Description
READ	0000 0011	Read data from memory array beginning at selected address
WRITE	0000 0010	Write data to memory array beginning at selected address
WREN	0000 0110	Set the write enable latch (enable write operations)
WRDI	0000 0100	Reset the write enable latch (disable write operations)
RDSR	0000 0101	Read STATUS register
WRSR	0000 0001	Write STATUS register
PE	0100 0010	Page Erase – erase one page in memory array
SE	1101 1000	Sector Erase – erase one sector in memory array
CE	1100 0111	Chip Erase – erase all sectors in memory array
RDID	1010 1011	Release from Deep power-down and read electronic signature
DPD	1011 1001	Deep Power-Dow

AT25M02 Instruction Set

Name	Format	Description
READ	0000 0011	Read from Memory Array
WRITE	0000 0010	Write to Memory Array
WREN	0000 0110	Set Write Enable Latch (WEL)
WRDI	0000 0100	Reset Write Enable Latch (WEL)
RDSR	0000 0101	Read Status Register (SR)
WRSR	0000 0001	Write Status Register (SR)
LPWP	0000 1000	Low Power Write Poll

Serial EEPROM Connected to Centronics Connector (Switches and LEDs)

Sharing the LED and Switch port, you loose two LEDs and one switch. Possible conflict with the bootstrap loader, if there is a read sequence (CS and read pattern 0000 0011). To prevent this, set the EEPROM into HOLD state e.g. with the WAIT signal.

SPI	MC (Master)	25LCxxxx (Slave)	Interface
MISO	J2.1 IN EF4	2 SO	diode e.g. 1N4148
MOSI	J2.11 O7 LED7	5 SI	direct
CLK	J2.10 O6 LED6	6 SCK	direct
CS	J2.12 O5 LED5	1 CS	direct
	P4.3 VDD	8 VCC	+5V capacitor 100 nF to GND
	"	3 WP	+5V
	J2.14 WAIT	7 HOLD	direct
	21 GND	4 GND	GND

Raspberry Pi can emulate SPI EEPROM. On RaspiElf the switches/LEDs are already connected to Raspi's GPIOs. No need for additional hardware. But I have to write an SPI server for the Raspberry Pi.

Raspi's SPI interfaces can't be used because of conflicting port usage.

• BCM 19 (SPI1 MISO) O5
• BCM 20 (SPI1 MOSI) -
• BCM 21 (SPI1 SCLK) shutdown
• BCM 18 (SPI1 CS0) CLR
• BCM 17 (SPI1 CS1) WAIT

• BCM 9 (SPI0 MISO) IN4
• BCM 10 (SPI0 MOSI) IN3
• BCM 11 (SPI0 SCLK) IN6
• BCM 8 (SPI0 CS0) IN7
• BCM 7 (SPI0 CS1) O0

Read Byte

CS0     EQU     0b1101111
CS1     EQU     0b0010000
CLK0    EQU     0b1011111
CLK1    EQU     0b0100000
DATA0   EQU     0b0111111
DATA1   EQU     0b1000000

        ; MSB first

READBYTE:
        LDI     0
        PLO     R5
        LDI     0xFF
        PHI     R6
        LDI     0xFF - 8
        PLO     R6
        SEX     R0
BITLOOP:
        OUT4,0b01000000      ; CLK for SPI 
        OUT4,0b00000000
        INC     R6
        GHI     R6           ; set CARRY
        SHRC
        GLO     R5
        B4      SETBIT       ; branch if bit set
        SHL                  ; bit not set
        BR      SAVEBIT      
SETBIT:
        SHLC
SAVEBIT:
        PLO     R5
        GLO     R6
        BNZ     BITLOOP

about 230 cycles for one byte -> 1 ms -> 1 KiB takes about 1 s @ 1.79 MHz

Write Byte

WRITEBYTE:
        LDI     0
        PHI     R6
        LDI     8
        PLO     R6
        SEX     R0
BITLOOP:
        GLO     R5           ; get the next bit
        SHLC                 , next bit is in the carry
        PLO     R5
        BDF     SETBIT
        OUT4,0b01000000      ; CLK for SPI with data bit cleared
        OUT4,0b00000000
        BR      NEXT
SETBIT:
        OUT4,0b11000000      ; CLK for SPI with data bit set 
        OUT4,0b10000000
NEXT:      
        DEC     R6
        GLO     R6
        BNZ     BITLOOP

Serial EEPROM patched on MC PCB

SPI Mode 0, data is always latched in on the rising edge of SCK and always output on the falling edge of SCK. For CS one output port bis is needed e.g. O7 or N2 (INP4) to start/end operation (A high-to-low transition on the CS pin is required to start an operation and a low-to-high transition is required to end an operation).

SPI	MC (Master)	25LCxxxx (Slave)	Interface
MISO	EF2	2 SO	direct
MOSI	D0	5 SI	direct
CLK	TPB & N1 (OUT2)	6 SCK	wired AND; Pullup 10 k, 2 1N4148
CS	N2	1 CS	direct
		8 VCC	+5V
		3 WP	+5V
	J2.14 WAIT	7 HOLD	direct
		4 GND	GND

Read Byte

        ; MSB first

        LDI     0
        PLO     R5
        LDI     0xFF
        PHI     R6
        LDI     0xFF - 8
        PLO     R6
        SEX     R6
BITLOOP:
        OUT2                 ; CLK for SPI, INC Rx
        GHI     R6           ; set CARRY
        SHRC
        GLO     R5
        B2      SETBIT       ; branch if bit set
        SHR                  ; bit not set
        BR      SAVEBIT      
SETBIT:
        SHRC
SAVEBIT:
        PLO     R5
        GLO     R6
        BNZ     BITLOOP

about 200 cycles for one byte -> 1 ms -> 1 KiB takes about 1 s

Write Byte

WRITEBYTE:
        LDI     0
        PHI     R6
        LDI     8
        PLO     R6
        SEX     R0
BITLOOP:
        GLO     R5           ; get the next bit
        SHLC                 , next bit is in the carry
        PLO     R5
        LSNF
        OUT2,0b00000000      ; CLK for SPI with data bit cleared
        LSDF
        OUT2,0b00000001      ; CLK for SPI with data bit set 
        DEC     R6
        GLO     R6
        BNZ     BITLOOP

Kermit/ZModem

What about using KERMIT or ZMODEM protocol for the file transfer and use the file system on the host? No need to add additional hardware (SD-card is anyway to modern You could use an old CP/M or even a PDP11 as host. The C-Kermit Local Server mode, e.g. MC can read/write the blocks as files block.0, block.2, block.255.

The serial communication is really slow, not only because of the 9600 baud, but you have to wait after each character to give CDP1802 some computation time.

https://github.com/utoh/pygmy-forth/blob/master/extras/kermit/pfkerm.doc

Spare Time Gizmo’s ELF2K ROM for RaspiElf

For details see Herb Johnson's ELF 2K ROM for 1802 Membership Card

v88.hex from the Spare Time Gizmos web site.

pi@cosmac:~/elf/elf2k $ cp v88.hex v88.hex.org
pi@cosmac:~/elf/elf2k $ patch v88.hex v88-mc.patch
pi@cosmac:~/elf/elf2k $ hex2bin v88.hex
hex2bin v2.5, Copyright (C) 2017 Jacques Pelletier & contributors

Allocate_Memory_and_Rewind:
Lowest address:   00000000
Highest address:  00007FFF
Starting address: 00000000
Max Length:       32768

Binary file start = 00000000
Records start     = 00000000
Highest address   = 00007FFF
Pad Byte          = FF
pi@cosmac:~/elf/elf2k $ bin2elf -s 8000 v88.bin 
0x8000 bytes written
pi@cosmac:~/elf/elf2k $ bin2elf -w -r LBR_8000.bin
0x0003 bytes written
pi@cosmac:~/elf/elf2k $ 

But there is "Post Code 88" -> SRAM size wrong

My MC has 64 KiB RAM and no ROM. But the RAM Size Test (part of monitor) expects ROM from 0x8000.

Herb Johnson wrote:

Peter, hopefully you can take it from here, find the BOOTS.ASM code at the link below, and "patch" it to accept an appropriate area for RAM. More than I can figure out today.

http://www.sparetimegizmos.com/Downloads/v88-source.zip