Overview
ISO/IEC 1863:1990 specifies a format and recording standard for 9‑track, 12.7 mm (0.5 in) wide magnetic tape used for data interchange. The standard defines recording method, tape and reel characteristics, track layout, block structure and error‑control conventions for systems using the ISO 7‑bit coded character set (ISO 646) or its 7‑/8‑bit extensions (ISO 2022, ISO 4873). It is primarily focused on NRZI (Non‑Return‑to‑Zero, Change‑on‑ones) recording at a nominal density of 32 ftpmm (800 ftpi) (actual 31.5 ftpmm).
Key topics and technical requirements
- Recording method and density
- NRZI recording; nominal density 32 ftpmm (800 ftpi), actual 31.5 ftpmm (800 ftpi).
- Nominal flux transition spacing: 31.75 µm (1 250 µin).
- Track configuration
- Nine longitudinal tracks with specified centerline offsets from the reference edge.
- Bit allocation: track 7 always ZERO; track 4 is parity (odd parity for characters).
- Block and file format
- Data blocks contain a data portion (minimum 18, maximum 2 048 characters), followed by a CRC character and an LRC character.
- Tape Mark format and use are specified (control block + CRC/LRC components).
- Error control
- Hardware CRC generation (generator polynomial and CRC register behavior are normative in Annex A).
- LRC used to maintain longitudinal parity across block characters.
- Signal and calibration
- Standard Reference Amplitude derived from a Master Standard Reference Tape (NIST SRM reference used for calibration).
- Interchanged tape average amplitude must be 70%–115% of Standard Reference; per‑transition limits (min 35%, max 120% of half the Standard Reference on first read pass).
- Erasure, gaps and handling
- Full tape DC erasure with specified erase direction and residual limits.
- Gap lengths specified: initial gap 76 mm min to 7 600 mm max; interblock gap nominal 15 mm (12.7 mm min, 7 600 mm max); CRC/LRC gaps defined.
- Wind tension 2.0–3.6 N and environmental conditioning (operating temp 16–32 °C, RH 20%–80%).
- Quality and calibration
- Limits on skew, track width, static skew, and allowed number of elongated gaps.
- Reference and secondary reference tapes (Master and SRM 3200) for calibration.
Applications and users
- Legacy mainframe and midrange data interchange between systems and vendors.
- Tape manufacturers, reel and head designers, and hardware vendors implementing 9‑track drives.
- Data archivists, digital preservation specialists and migration teams working with historical tape media.
- Calibration labs and test houses using NIST reference tapes for amplitude and recording tests.
- Systems integrators restoring or emulating vintage data workflows.
Related standards
This standard remains essential for interoperability, reliable reading/writing and preservation of legacy 9‑track magnetic tape data. Keywords: ISO/IEC 1863:1990, 9‑track magnetic tape, 12.7 mm, NRZI, 32 ftpmm, 800 ftpi, CRC, LRC, tape interchange, NIST reference.
Open preview (PDF)Information processing — 9-track, 12,7 mm (0,5 in) wide magnetic tape for information interchange using NRZ1 at 32 ftpmm (800 ftpi) — 32 cpmm (800 cpi)
