Page 172 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

7.4 Finished speech-recognition circuit

From
74LS373
OR
19
16 151

Disable High
2
AND Enable Low
Error Code Detection from MSB of 74LS373
7.5 Error detection circuit taken from upper BCD number

The second way to work around the problem is to simply use a PIC
microcontroller to read the entire 8-bit output from the SRC. Any
word number above 40 is an error and should be ignored. While we
are not interfacing this circuit to a microcontroller here, it should
be evident to anyone who has worked with the PICBASIC compiler
and PIC chips (see Chap. 6) in other applications that this inter-
face would not present a problem. In Chap. 15 we use a PIC inside
the speech-controlled circuit for controlling a robotic arm.

The 8-bit output is taken from the output of the 74LS373 data octal
latch. The output is not a standard 8-bit byte, but it is broken into
two 4-bit binary coded decimal (BCD) nibbles. BCD code is related
to standard binary numbers as Table 7.1 illustrates.
Team LRN Speech-controlled mobile robot