RCA 301, Programmer'S Reference Manual

Page: 11 / 235

Application of Accuracy Checking Techniques
Program Control —The following controls are typical of conditions causing the computer to stop:
1. Incorrect parity in Memory Address Register.
2. Incorrect parity in Memory Register.
3. Incorrect parity in Operation Register.
4 . Incorrect parity in N Register.
5. Incorrect parity in Repeat (N
R
) Register.
Input I Output —The following are input/output conditions which may cause the Computer to stop:
1. Incorrect parity of data being transferred.
2. Input/Output device inoperable or not following command.
3. Record not on turntable of Data Record File.
4. Attempting to write to record or magnetic tape when lockout device applied.
5. Card equipment input hopper empty or output hopper full.
6. Non-RCA 301 card character read by the Card Reader, when in the Translate Mode.
7. Tape Station reading extra bits in interblock gap.
8. On-Line Printer paper supply low.
THE RCA 301 CODE
The RCA 301 System employs a binary code using seven binary digits, or bits to represent each RCA 301
character. Of the seven bits which make up each of the characters, the highest order bit (2
6
) is the parity bit. The
remaining six bits are the information bits, with a specific configuration of bits representing each RCA 301 character.
Bit Position
P
2
s
2" 2
3
2
J
V
2°
Bits
X X X X X
X X
(X = 0 or 1)
For ease in presentation, the bit configurations of the RCA 301 Code are divided into four groups with the
zone bits (2
5
and 2
4
) designating the group, as follows:
RCA 301 GROUP CODE
2
5
2
4
2
3
2
2
2'
2°
Group 1 0 0 X X X
X
Group II
0 1 X X
X X
Group III 1 0 X X X
X
Group IV
1 1 X X
X
X
1-5