The Sysdata JR computer is a Brazilian clone of the Tandy TRS-80 Model 1.
Within the white molded plastic case, is a single printed circuit board equipped with a Z80A 8-bit CPU cadenced at 1.78MHz. It can operate at 3.56MHz through an optional modification.
The 12 KB ROM memory includes the OS and BASIC Level II interpreter. There is also a 2 KB EPROM (socketed) for additional chips. For example, it could be used for extension of the operating system and BASIC interpreter, called EXTENDED BASIC, which had fourteen additional commands, many of them available only on Disk BASIC.
The basic model of the JR is delivered with 16 KB RAM but can be internally expanded up to 48 KB (64 KB in the disk version).
At the rear of the computer is the system bus (standard S80 with fifty data lines). There can also be found connectors for two cassette recorders (!), composite video output, RF video output and voltage selection switch (110/220V), ON/OFF switch, RESET button and video mode switch (normal/inverse).
Through the expansion bus, dot matrix printers could be connected, through a standard Centronics parallel interface; RS-232C type programmable interface card, asynchronous serial (modem connection point for telephone line), real-time clock card, voice synthesizer, Atari type joystick and optical pen.
The standard auxiliary memory device is the common audio cassette recorder (500 baud). The JR can control up to two recorders simultaneously through separate connections for EAR (read), MIC (write) and REMOTE (for motor control).
If you want to use 5.25-inch floppy disk drives, you must add a controller board to the expansion bus, which has a capacity of up to four 5.25" or 8" floppy disk drives, single or dual-density. The single-density drive has 100KB capacity per floppy disk, while the dual-density drive has 184KB capacity.
The basic model includes BASIC Level II language. You can use other languages from tapes such as ASSEMBLER Z80 (ADTASM), Tiny PILOT, Tiny PASCAL, etc. With a disk drive you can use more powerful languages, including BASIC interpreters and compilers, FORTRAN, COBOL, PASCAL, FORTH, RPG, ALGOL, etc. Some basic utilities are included in the SYSDOS operating system. With the CP/M 2.2 operating system, a large number of software was also available.
The keyboard is of calculator type with flat square rubber keys which makes typing difficult. There is also a professional version of the JR computer with an mechanical keyboard. Control keys allow program interruption (BREAK), screen clearing (CLEAR), cursor movement, upper/lower case, etc.
The video unit can be either a regular TV (black and white or color), with modulated RF output, connected directly through the external antenna, or a professional monochrome video monitor connected to the composite video output (simultaneous connection is possible !).
The graphics capability of JR Sysdata is the same as the TRS-80, i.e. low resolution of 128x48, individually addressable pixels. With the additional EPROM option, the character generator incorporates upper and lower case letters, in addition to 64 semigraphic characters, and also makes available another 96 characters, which can eventually be redefined (?).
This computer was followed by the JR III, compatible with the Tandy TRS-80 Model III.
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Thanks to mci.org.br for most info.
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