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Sharp PC-1211

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Sharp PC-1211
Sharp PC-1211
A PC-1211 switched on, with its name on the display (photo: Yagshi, CC BY 3.0)
Specifications
ManufacturerSharp Corporation
TypePocket computer
ReleasedMarch 1980[1]
CPUTwo Sharp processors, SC43157 (CPU I) and SC43178 (CPU II)[2]
Memory1,424 program steps; 26 fixed data memories plus up to 178 sharing the program area[3]
Storage—
Display24-character 5 × 7 dot matrix LCD[3]
Sound—
PowerFour MR44 1.35 V mercury cells (5.4 V), 0.011 W; about 300 hours[4][3]
Dimensions175 × 70 × 15 mm[4]
WeightAbout 170 g[4]
OS / Firmware—
Model no.PC-1211; sold by Radio Shack as the TRS-80 Pocket Computer (PC-1)

The Sharp PC-1211 is a pocket computer that Sharp Corporation released in March 1980. It is programmed in BASIC and has a 24-character liquid crystal display and memory for 1,424 program steps, and it runs from four mercury button cells.[1][3] Radio Shack sold the same machine from July 1980 as the TRS-80 Pocket Computer, later called the PC-1, with black outer plastics and a grey display frame.[1]

Hardware

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Sharp's service manual lists the system as two processors, CPU I (SC43157) and CPU II (SC43178), each with internal ROM; three 4 Kbit TC5514P RAMs; three SC43125 display chips, each with built-in RAM; TC4011UBP, TC4019BP, TC4069BP and TC4066BP logic; the 24-digit LCD; the keyboard; and a CSB2560 crystal.[5] The parts list gives the LCD as the LF8017JE.[2] Wikipedia gives the processors as the SC43177 and SC43178, running at 256 kHz. The service manual uses SC43157 for CPU I throughout, in the system configuration, the LSI descriptions and the parts list.[1][5][2] A 9-pin connector takes the CE-121 cassette interface or the CE-122 printer.[2][1]

The CMOS memory is kept alive by the batteries, so programs and data stay in memory when the computer is switched off.[4] Sharp's service manual gives the current drawn from a 4.72 V supply as under 850 µA after pressing ON and under 12 µA after pressing OFF.[6]

Batteries

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Sharp specifies four MR44 1.35 V mercury cells, giving about 300 hours of use.[4][3] The instruction manual says the computer cannot be operated on silver oxide or alkaline manganese cells, even though they are the same shape, and that all four cells must be replaced together.[4] A grey dot in the upper right corner of the display is the battery indicator: when it goes out, the batteries need replacing.[4] Sharp's procedure:[4]

  1. Switch the computer off.
  2. Remove the screws from the back cover with a small screwdriver. Two kinds of screw are used.
  3. Replace all four cells.
  4. Hook the tabs of the back cover into the slits in the case. Push the cover in slightly while refitting the screws, and tighten them securely.
  5. Press the reset switch on the back cover with a ball-point pen, then clear the computer from the keyboard as the manual describes.

Sharp advises removing the batteries if the computer is to be stored, to avoid damage from leakage.[4] For cleaning up after a leak, see Battery Explosion, Capacitor or Corrosion Damage.

Opening the case

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Sharp's service procedure:[6]

  1. Remove the two screws (a) and the two screws (b) from the lower cabinet.
  2. Separate the upper and lower cabinets, starting from the screw side. They are latched together at three points.
  3. The back of the arithmetic board is now visible, and CPU II can be reached. To reach CPU I, remove the buzzer, held by screw (c).
  4. To check the key board, remove screws (d) and (e) and fold the arithmetic board up to a right angle.
  5. To remove the key board from the upper cabinet, take out the nine screws (f) and the two screws (g). The key tops can fall out when the board comes away.

Before desoldering a chip on the key board, take the board out of the upper cabinet: the heat can deform the rubber key mat.[6]

All Reset switch

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Strong electrical noise can leave every key dead, including the CA/BREAK/ON key. So can connecting or disconnecting the CE-121 with the computer switched on. The All Reset switch on the back panel clears the condition, but it erases all programs and data.[4] Clean the case with a soft, dry cloth; Sharp warns against solvents and wet cloths.[4] The instruction manual gives the automatic power-off time as about seven minutes; the service manual gives about six.[4][3]

Peripherals

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  • The CE-121 cassette interface records and loads programs and data on an ordinary cassette recorder. Three AA cells in the CE-121 power its remote control of the recorder, which switches the recorder's REMOTE socket through a relay.[4][7] Sharp's service manual covers it, with a check procedure for its recording and playback circuits.[7]
  • The CE-122 printer.[1]

Documentation

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  • File:Sharp PC-1211 and CE-121 Service Manual.pdf: Sharp's service manual for the PC-1211 and the CE-121, with specifications, block diagrams, LSI signal descriptions, servicing notes, the check program, circuit diagrams and parts lists.[3]
  • The English instruction manual is on the Internet Archive.[4] So is Radio Shack's service manual for the TRS-80 PC-1 and its cassette interface.[8]
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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Sharp PC-1211, Wikipedia—link(accessed 2026-10-21) Released by Sharp in March 1980; the TRS-80 Pocket Computer (later called the PC-1) is a badge-engineered version sold by Radio Shack from July 1980, with black rather than brown outer plastics and a grey display frame; SC43177 and SC43178 processors at 256 kHz; three TC5514P 4 Kbit RAMs; CE-121 cassette interface and CE-122 printer.
  2. ↑ 2.0 2.1 2.2 2.3 Sharp Corporation, Service Manual, Model PC-1211, CE-121 (File:Sharp PC-1211 and CE-121 Service Manual.pdf), PC-1211 parts list and guide, printed pages 32 and 33 (PDF pages 38 and 39): LCD LF8017JE; SC43125 display chips; SC43157 (CPU I); SC43178 (CPU II); TC5514P (RAM); TC4011UBP, TC4019P, TC4066P and TC4069P; crystal; buzzer; all reset switch; 9-pin connector; battery terminals; capacitors including one 1 µF 50 V aluminium electrolytic.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Sharp, PC-1211 / CE-121 service manual (File:Sharp PC-1211 and CE-121 Service Manual.pdf), specifications, printed pages 2 and 3 (PDF pages 2 and 3): display LF8017JE, 5 × 7 dot liquid crystal, 24 columns; 12-digit mantissa and 2-digit exponent; program memory 1,424 steps maximum; 26 fixed data memories and up to 178 flexible memories shared with the program memory; 18 reserve programs, 48 steps maximum; BASIC; four MR44 mercury batteries, 300 hours; automatic power off after about 6 minutes; audio cassette unit as the peripheral.
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 Sharp Corporation, PC-1211 Instruction Manual (English), Manual: PC1211 OM SHARP EN, Internet Archive—link(accessed 2026-10-21) Care: clean with a soft, dry cloth, no solvents or wet cloth; remove the batteries if the computer is not to be used for a long time; strong external noise can make all keys inoperative, including the CA/BREAK/ON key, cleared with the All Reset switch on the back panel, which erases memory and programs. Battery indicator: a grey dot in the upper right corner of the display; when it is off, replace the batteries. Battery replacement: turn off, remove the back cover screws with a small screwdriver (two kinds), replace the batteries, hook the tabs of the back cover into the slits, push the cover in slightly while refitting and tightening the screws, press the reset switch on the back cover with a ball-point pen, then clear the computer; replace all four at once, do not mix new and used cells; the computer cannot be operated on silver oxide or alkaline manganese cells, although they are similar in shape; mercury battery type MR44, 1.35 V, × 4. Specifications: CMOS battery back-up of program, data and reserve memories; 5.4 V DC, 0.011 W, or 0.013 W with the CE-121; about 300 hours with MR44 cells at 20 °C; 0 to 40 °C; 175 × 70 × 15 mm; about 170 g; auto power off after about 7 minutes. CE-121: three UM-3 (AA, R6) cells drive the tape recorder remote control; turn the computer off before connecting or disconnecting it, or the keys may lock and need the All Reset switch.
  5. ↑ 5.0 5.1 Sharp, PC-1211 / CE-121 service manual (File:Sharp PC-1211 and CE-121 Service Manual.pdf), "System configuration" and section 2-1, printed page 5 (PDF page 5): CPU I (SC43157) × 1; CPU II (SC43178) × 1; 4K-bit RAM (TC5514P × 3); display chip (SC43125 × 3, with built-in RAM); 2AND gate (TC4011UBP × 1); 2AND 2OR (TC4019BP × 1); inverter (TC4069BP × 1); quad analog switch multiplexer (TC4066BP); LCD (24-digit dot LCD); key; crystal (CSB2560); the CPUs are provided with internal ROM. Section 3-1, printed page 12 (PDF page 12), is headed "SC43157 (CPU I)".
  6. ↑ 6.0 6.1 6.2 Sharp, PC-1211 / CE-121 service manual (File:Sharp PC-1211 and CE-121 Service Manual.pdf), "About servicing", printed page 17 (PDF page 17): disassembly (remove two screws (a) and two screws (b); separate the upper cabinet from the lower cabinet from the screw side, as they are latched together at three points A, B and C); repair procedure (the back of the arithmetic board is visible once the lower cabinet is removed; CPU II can be replaced; to check the key board, bend the arithmetic board to a right angle after removing screws (d) and (e); CPU I can be inspected after removing the buzzer, held by screw (c); the key board comes off the upper cabinet after removing nine screws (f) and two screws (g), and the key tops may fall out); LSI replacement (Sharp's LSI soldering pencil UKOG-0078CSZZ; remove the key board from the upper cabinet before desoldering an LSI on it, or the heat may deform the key rubber; cut the legs of an IC that is removed); current consumption at 4.72 V: under 850 µA after ON, under 12 µA after OFF.
  7. ↑ 7.0 7.1 Sharp, PC-1211 / CE-121 service manual (File:Sharp PC-1211 and CE-121 Service Manual.pdf), cassette operation, printed pages 18 to 24 (PDF pages 18 to 24): recording format; recording signal of about 4 kHz for "1" and about 2 kHz for "0", passed through the CE-121 to the recorder's MIC input; playback from the EAR socket through an amplifier and Schmitt circuit to CPU II; the CE-121 controls the REMOTE terminal through a relay switched by a TC4528P monostable; cassette check procedure.
  8. ↑ TRS-80 PC-1 Pocket Computer and Cassette Interface Service Manual, Internet Archive—link(accessed 2026-10-21)


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