Yet another computer museum - The Epson HX-20

Top Epson HX-20 top Standard 16 kByte RAM, here with the expansion unit, another 16 kByte. All battery operated.
More info in this announcement from Practical Computing magazine October 1982.
Targeted as a field terminal it found other uses like wordprocessing. The successor was the PX-8 which combined advantages from the QX-10 (CP/M, wide screen) with the HX-20 portability.

Inside Epson HX-20 board Epson boards usually have names. The HX-20 board name is 'MOSU'.
The BASIC 'PRINT FRE(0)' command should return 12891 bytes free for a non-expanded HX-20.
The standard ROMs map from FFFFh to 8000h, the empty socket is for the option ROM (6000h-7FFFh)

Expansion unit board Epson HX-20EU Expansion Unit board The Expansion Unit contains 16 kByte RAM, constructed of eight 2kByte static RAM chips. The two ROM sockets are default empty. With the Expansion Unit connected, and no programs loaded the BASIC 'PRINT FRE(0)' should return 29275 bytes free (use Ctrl-@ to initialize). See the memory map for more info on the HX-20 memory map with and without the Expansion Unit.
More information is in the HX-20 Technical Support Manual, see Virtual Library or Using the Epson HX-20 expansion unit

ROM Cartridge ROM Cartridge module The cassette bay could also be used for the ROM cartridge. A 32 kByte max ROM can contain up to 32 files which are listes and read via the FILES "PAC0:" and LOAD "PAC0:filenaam" commands in Basic. Other ROM structures were also possible, but would need additional software.
This ROM is not directly mapped into memory, data is loaded into memory first.
HX-20 ROM cartridge; file format

Batteries Nowadays not much of the original battery packs for the HX-20 will be in good working order. With some trouble and quite a sum of money, you can still buy replacements or make one yourself from NiCD C-cells. For operating the HX-20 only once in a while, this is not very cost effective. Replacing the internal pack with an external set of modern penlight (AA) NiHM cells works just as good, but has its price; making an extra hole or leaving out the connector pane. The battery is an essential part of the power supply; charging keeps the adapter voltage in check. Without it, the voltage on the circuit board becomes much too high and using power hungry peripherials lead to the 'CHARGE BATTERY!' message.

Disk drive unit Another expansion option of the HX-20 is the TF-20 floppy disk unit. This unit needs a floppy to load its own OS (CP/M) into RAM, and then could serve as disk drive for the HX-20, PX-8 or PX-4. The HX-20 retrieves a disk basic extension from the drive when entering BASIC. See the Epson TF-20 page for more info on the TF-20.

Printer ERC-05 printer ribbon cartridge The printer uses a ribbon cartridge found in lots of small Epson printers. The black ones are ERC-05 (F601354020) and show up at Ebay regularly. It can also be used for PX-4 and PX-16 printers.

Connect to PC
HX-20 PC PC 8-pin DIN 9-pin subDE 25-pin subDB function 1 -------- 5 --------- 7 GND 2 -------- 2 --------- 3 HX-20 TxD, PC RxD 3 -------- 3 --------- 2 HX-20 RxD, PC TxD 7 -+ 4 -+ | | RTS - CTS loop 8 -+ 5 -+ 6 -+ 6 -+ | | 1 -+ 8 -+ DSR, CD, DTR loop | | 4 -+ 20 -+

To connect the HX-20 to a PC, I use an Epson #705 cable, a gender changer, a null modem adapter and a 25p to 9p adapter. In essence it boils down to this diagram. Note that the DIN pin numbering is not regular.
Text (BASIC) transfer from PC to HX-20:

set serial port speed to 1200 Baud: Linux: sudo /bin/stty -F /dev/ttyUSB0 ospeed 1200 ispeed 1200
enter into HX-20: LOAD "COM0:(48N1F)" <ENTER>
send file: Linux: sudo cat fileName > /dev/ttyUSB0 and wait for it to finish
press <BREAK> on HX-20. The program is now loaded.

Text (BASIC) transfer from HX-20 to PC:

start terminal program and set serial port to 4800 Baud
start text capture mode
enter into HX-20: LIST "COM0:(68N1F)" <ENTER> and wait for it to finish
save captured text

Local links:

Announcement in Practical Computing October 1982,
Wordprocessors for the HX-20,
Scanned and PDFed doc,
Info on the HOOAAG adapter,
Info on the QX-10 computer ,
Info on the PX-8 computer. An newer machine of similar architecture, but CP/M based,
Info on the PX-4 computer. The PX-4 can be seen as the successor of both the HX-20 and PX-8,
Info on the TF-20 disk drive system. A CP/M based disk station,
Epson serial protocol for external devices like disk drives and monitors (preliminary),
Epson type numbers and codes.

Generic links:

Last update: 2010-02-13

fjkraan@xs4all.nl

Top		Standard 16 kByte RAM, here with the expansion unit, another 16 kByte. All battery operated. More info in this announcement from Practical Computing magazine October 1982. Targeted as a field terminal it found other uses like wordprocessing. The successor was the PX-8 which combined advantages from the QX-10 (CP/M, wide screen) with the HX-20 portability.
Inside		Epson boards usually have names. The HX-20 board name is 'MOSU'. The BASIC 'PRINT FRE(0)' command should return 12891 bytes free for a non-expanded HX-20. The standard ROMs map from FFFFh to 8000h, the empty socket is for the option ROM (6000h-7FFFh)
Expansion unit board		The Expansion Unit contains 16 kByte RAM, constructed of eight 2kByte static RAM chips. The two ROM sockets are default empty. With the Expansion Unit connected, and no programs loaded the BASIC 'PRINT FRE(0)' should return 29275 bytes free (use Ctrl-@ to initialize). See the memory map for more info on the HX-20 memory map with and without the Expansion Unit. More information is in the HX-20 Technical Support Manual, see Virtual Library or Using the Epson HX-20 expansion unit
ROM Cartridge		The cassette bay could also be used for the ROM cartridge. A 32 kByte max ROM can contain up to 32 files which are listes and read via the `FILES "PAC0:"` and `LOAD "PAC0:filenaam"` commands in Basic. Other ROM structures were also possible, but would need additional software. This ROM is not directly mapped into memory, data is loaded into memory first. HX-20 ROM cartridge; file format
Batteries		Nowadays not much of the original battery packs for the HX-20 will be in good working order. With some trouble and quite a sum of money, you can still buy replacements or make one yourself from NiCD C-cells. For operating the HX-20 only once in a while, this is not very cost effective. Replacing the internal pack with an external set of modern penlight (AA) NiHM cells works just as good, but has its price; making an extra hole or leaving out the connector pane. The battery is an essential part of the power supply; charging keeps the adapter voltage in check. Without it, the voltage on the circuit board becomes much too high and using power hungry peripherials lead to the 'CHARGE BATTERY!' message.
Disk drive unit		Another expansion option of the HX-20 is the TF-20 floppy disk unit. This unit needs a floppy to load its own OS (CP/M) into RAM, and then could serve as disk drive for the HX-20, PX-8 or PX-4. The HX-20 retrieves a disk basic extension from the drive when entering BASIC. See the Epson TF-20 page for more info on the TF-20.
Printer		The printer uses a ribbon cartridge found in lots of small Epson printers. The black ones are ERC-05 (F601354020) and show up at Ebay regularly. It can also be used for PX-4 and PX-16 printers.
Connect to PC	HX-20 PC PC 8-pin DIN 9-pin subDE 25-pin subDB function 1 -------- 5 --------- 7 GND 2 -------- 2 --------- 3 HX-20 TxD, PC RxD 3 -------- 3 --------- 2 HX-20 RxD, PC TxD 7 -+ 4 -+ \| \| RTS - CTS loop 8 -+ 5 -+ 6 -+ 6 -+ \| \| 1 -+ 8 -+ DSR, CD, DTR loop \| \| 4 -+ 20 -+	To connect the HX-20 to a PC, I use an Epson #705 cable, a gender changer, a null modem adapter and a 25p to 9p adapter. In essence it boils down to this diagram. Note that the DIN pin numbering is not regular. Text (BASIC) transfer from PC to HX-20: set serial port speed to 1200 Baud: Linux: sudo /bin/stty -F /dev/ttyUSB0 ospeed 1200 ispeed 1200 enter into HX-20: LOAD "COM0:(48N1F)" <ENTER> send file: Linux: sudo cat fileName > /dev/ttyUSB0 and wait for it to finish press <BREAK> on HX-20. The program is now loaded. Text (BASIC) transfer from HX-20 to PC: start terminal program and set serial port to 4800 Baud start text capture mode enter into HX-20: LIST "COM0:(68N1F)" <ENTER> and wait for it to finish save captured text