Apple-1 Operation Manual 1976

Apple Computer Company, Apple-1 Operation Manual, 1976, 15 pages. Issued from Apple Computer Company, 770 Welch Road, Palo Alto, California. This is Apple's only manual for the Apple I, and it is the primary source for every published figure about the machine.

Contents

• Specifications — one page, the whole published specification of the machine.
• Section I — Getting Started: keyboard connection (the "DIP" keyboard connector at

 B4, seven data lines, strobe of either polarity and either duration), display
 connection (Molex J2), AC power sources (Molex J1), and a four-step test
 program.

• Section II — Using the System Monitor: the monitor's command syntax and the complete

 commented assembly listing of the 256-byte monitor PROM at $FF00–$FFFF.

• Section III — How to Expand the Apple System: the 44-pin edge connector, DMA, refresh

 timing, the PIA register map, and circuits for single-step, slow-ROM and address display.

• Schematics: drawing 00101, sheets 1–3 of 3, the third sheet being the power

 supply.

Apple's published specification

Apple-1 Operation Manual, specifications page

Item	Apple's figure
Microprocessor	MOS Technology 6502
Clock frequency	1.023 MHz
Effective cycle frequency	0.960 MHz (including refresh waits)
Video output	Composite positive video, 75 Ω, level adjustable between zero and +5 V p-p
Line rate	15,734 Hz
Frame rate	60.05 Hz
Format	40 characters/line, 24 lines, with automatic scrolling
Display memory	Dynamic shift registers (1 K × 7)
Character matrix	5 × 7
RAM	16-pin, 4 K dynamic, type 4096 (2104)
On-board RAM capacity	8 KB (4 KB supplied)
Power supplies	+5 V @ 3 A, ±12 V @ 0.5 A, −5 V @ 0.5 A
Input power	8–10 V AC (RMS) @ 3 A and 26–28 V AC (RMS) centre-tapped @ 1 A
Recommended transformers	Stancor P-8380 or Triad F31-X; Stancor P-8667 or Triad F40-X

What this document settles

The display is not memory-mapped. Apple's own specification gives the display memory as "dynamic shift registers (1 K × 7)". There is no screen buffer in the 6502 address space, and the only display hardware visible to software is the PIA: $D012 DSP data (lower seven bits are data out, the high bit is a "display ready" input, 1 = ready, 0 = busy) and $D013 DSP control. The keyboard is $D010 KBD data (high-order bit equals 1) and $D011 KBD control (high-order bit indicates "key ready"; reading the key clears the flag, the rising edge of the keyboard strobe sets it).

Where the 0.960 MHz comes from. "Four out of every 65 clock cycles is dedicated to memory refresh." RF goes low 150 ns after the leading edge of ϕ1 and stays low for one clock cycle; ϕ2 is inhibited during a refresh cycle and the processor is held in ϕ1. Dynamic memory added off-board should be clocked from ϕ0, which is ϕ2 except that it continues through a refresh cycle; a PIA is unaffected, because it reacts to ϕ2 only.

The edge connector is dangerous if it is misread. Only +5 V is regulated there. The pins for +12 V, −12 V and −5 V carry raw DC of approximately ±14 V, external regulators must be used, and Apple writes: "Exercise great care in the handling of the raw DC, as no short-circuit protection is provided." Address lines are TTL buffered and the data lines drive ten equivalent capacitive loads (one TTL load and 130 pF) without external buffering. The board itself draws no more than 1.5 A from the +5 V supply against a regulator rated 3 A, so 1.5 A is available for expansion if the transformer will supply it. For DMA, the solder jumper marked DMA must be broken. Apple describes the system as "fully expandable to 65K".

A diagnostic in one line. Pressing RESET should display "backslash — return". Apple: "A backslash alone (cursor remains on same line as backslash) indicates bad page RAM" — that is, bad page-zero RAM, which the monitor needs before it can do anything else.

The monitor's real command set. Commands are typed a line at a time, up to 128 characters, and nothing executes until RETURN is typed.

• : — store: 300: A9 00.
• . — the range delimiter, not a register display:

 4F.52 56 58.5A dumps three blocks. The monitor has no register display.

• R — run a program at the most recently opened address.
• ESC — cancels the line and echoes backslash-return.
• SHIFT-O (backarrow) — backspaces and echoes an underline.
• A blank or comma is a delimiter only; a string of them behaves as one.

Apple's own four-step test program, which exercises keyboard, display and supplies together, is: RESET, then :A9 AA 20 EF FF E8 8A 4C 2 0 RETURN, then .A RETURN to list it back, then R RETURN — which prints a continuous stream of ASCII characters until RESET is pressed.

Related

• Apple I — the machine this manual documents
• Apple II Schematics — the addendum to the Apple II Reference Manual
• Apple II Reference Manual