In The Unicode Standard, Ethiopic script implementation is discussed in  Chapter 19 Africa.

Ethiopic script was first encoded in The Unicode Standard version 3.0. Since that time the encoding has undergone a number of modifications; the script is now encoded in the following blocks:

BlocksCharacter RangeAdded in Unicode VersionUnicode Charts
Ethiopic 1200..137F 3.0  U1200
Ethiopic Supplement 1380..139F 4.1  U1380
Ethiopic Extended 2D80..2DDF 4.1  U2D80
Ethiopic Extended-A AB00..AB2F 6.0  UAB00

Subsequent to version 3.0, the following characters have been added to the Ethiopic script:

CharactersUnicode VersionDocumentation
1207 4.1  n1846.pdf/ L2/04-143
1247 4.1  n1846.pdf/ L2/04-143
1287 4.1  n1846.pdf/ L2/04-143
12AF 4.1  n1846.pdf/ L2/04-143
12CF 4.1  n1846.pdf/ L2/04-143
12EF 4.1  n1846.pdf/ L2/04-143
130F 4.1  n1846.pdf/ L2/04-143
131F 4.1  n1846.pdf/ L2/04-143
1347 4.1  n1846.pdf/ L2/04-143
135D..135E 6.0  n3572.pdf/ L2/09-050
135F..1360 4.1  n1846.pdf/ L2/04-143
1380..1399 4.1  n2747.pdf/ L2/04-143
2D80..2D96 4.1  n1846.pdf/ L2/04-143
2DA0..2DA6 4.1  n1846.pdf/ L2/04-143
2DA8..2DAE 4.1  n1846.pdf/ L2/04-143
2DB0..2DB6 4.1  n1846.pdf/ L2/04-143
2DB8..2DBE 4.1  n1846.pdf/ L2/04-143
2DC0..2DC6 4.1  n1846.pdf/ L2/04-143
2DC8..2DCE 4.1  n1846.pdf/ L2/04-143
2DD0..2DD6 4.1  n1846.pdf/ L2/04-143
2DD8..2DDE 4.1  n1846.pdf/ L2/04-143
AB01..AB06 6.0  n3572.pdf/ L2/09-050
AB09..AB0E 6.0  n3572.pdf/ L2/09-050
AB11..AB16 6.0  n3572.pdf/ L2/09-050
AB20..AB26 6.0  n3572.pdf/ L2/09-050
AB28..AB2E 6.0  n3572.pdf/ L2/09-050

Documentation refers to  ISO Working Group and Unicode proposals

A number of proposals for its inclusion have been submitted to the Unicode Technical Committee and WG2:

1992-11-25 Unicode Technical Report #1 — Joe Becker ( TR1)

1997-01-28 Combined PDAM registration and ballot for FPDAM 10: Ethiopic script — Bruce Paterson (L2/97-003 (not online))

1997-12-01 Report on JTC1/SC2 letter ballot on FPDAM No. 10 to ISO/IEC 10646-1 (Ethiopic Script) — SC2/WG2 ( WG2 N1630.doc, L2/97-276 (not online))

1998-09-11 Proposal to encode Ethiopic Extensions in the BMP of ISO/IEC 10646 (was distributed as L2/98-300) — Ethiopia, Ireland ( WG2 N1846,  L2/98-300, L2/00-081)

1999-03-31 Ordering labio-velar characters in Ethiopic — John Clews ( L2/99-122)

2000-08-25 Proposed glyph fixes for Ethiopic pages in ISO/IEC 10646-1:2000 — Michael Everson ( L2/00-282)

2003-08-22 Ethiopic Word Space U+1361 — Mark Davis ( L2/03-279)

2003-08-25 UTS #18, U+1361 Comments — Daniel Yacob ( L2/03-298)

2004-04-23 Revision of the N1846 Proposal to add Extended Ethiopic to the BMP of the UCS — Quality and Standards Authority of Ethiopia, Ethiopia ( WG2 N2747,  L2/04-143)

2004-06-18 Revisions proposed to N2747 (Extended Ethiopic) — Michael Everson, Daniel Yacob ( WG2 N2814,  L2/04-265)

2007-05-15 PR #96 Comment — Daniel Yacob ( L2/07-194)

2009-02-05 Proposal to Encode Additional Ethiopic Characters — Lorna Priest ( WG2 N3572,  L2/09-050)

2009-04-22 Report to JTC1 Chair and JTC1/SC2 Chair Regarding Resolution 34 on African Languages — Deborah Anderson ( WG2 N3641,  L2/09-285)

2015-05-02 Proposal to Reclassify Ethiopic Wordspace as a Space Separator (Zs) Symbol — Daniel Yacob ( L2/15-148)

Other documents related to Ethiopic and Unicode:

1999/Sept  A Roadmap to the Extension of the Ethiopic Writing System Standard Under Unicode and ISO-10646 — Asteraye Tsigie, Berhanu Beyene, Daniel Aberra, Daniel Yacob (IUC15)

2001-Sept  Considering Ethiopic Character Classes — Daniel Yacob (IUC19)

2004-Mar/April  The Foundation for Indigenous ICT in Ethiopia — Daniel Yacob (IUC25)