Programming instructions

An alphanumeric character is one line (5, 7, or 8 holes) on tape. A binary
word consists of three consecutive characters (18 bits) on tape which have
the 8th hole present. Only 8-hole tape is used in the binary mode; the 7th
hole is ignored. The first, second, and third six-bit characters are the left,
middle, and right thirds, respectively, of the 18-bit word. The reader
commands, iot select series 01, are:
rsf - 700101 - Skip if Reader flag is a 1, i.e., character or word present.
rsa - 700104 - Select Reader and fetch one alphanumeric character from
tape. Clear the Reader flag. Reset RB. The character is read
into RB bits 10-17. Turn on the Reader flag when character
is present.
rsb - 700144 - Select Reader and fetch a binary word from tape. Clear the
Reader flag. Reset the RB. Fetch the next three characters
(with 8th holes present) from perforated tape and place in
RB bits O-5, 6-11, and 12-17. Turn on Reader flag when a
word is assembled.
rrb - 700112 - Read RB. Clear the Reader flag, and transfer the contents of
RB to the AC.
rcf - 700102 - Clear the Reader flag. C(RB) v C(AC) => C(AC)
The Reader flag is connected to the Program Interrupt Control and to bit 0
of the iors instruction. Several methods may be used to program the
Reader. The following sequence reads a character from tape and places it
in the AC. Up to 400 microseconds of computation time are available
betkeen the end of the sequence and the next command to read a character
or word from tape. The sequence, starting in register 40 is:
PROGRAM SEQUENCE
/perforated-tape reader
W
rsa
/select reader alphanumeric
rsf /begin loop to look for character arrival
Jmp 41
/end loop to look for arrival
rrb /fetch character from reader buffer
By changing instruction 40 to rsb the sequence would fetch a binary word.
PRINTER-KEYBOARD AND CONTROL, TYPE 65
The Printer-Keyboard is a Teletype Model 28 KSR (keyboard send-receive)
which can print or receive ten characters per second. A five-bit code, given
in Appendix 2, represents the characters. The printing (output) and key-
board (input) functions have separate commands and control logic.
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