Book is “The AVR Microcontroller and Embedded System, Using C & Assembly”
peterbjornx or bootnecklad should be able to answer this fairly easily
Question 49:
“Using the 74138, design memory decoding circuitry in which the memory block controlled by Y0 is in the 0000h to 3FFFh space. Indicate the size of the memory block controlled by each Y.”
This is confusing to me because it doesn’t state how many address pins I am suppose to use. All of the examples in the book in this section are using 16 address pins (A0-A15) so I assume I should only use 16 pins then is this always true, the examples are using SRAM and ROM?
This is the answer I have come up with now
The size of each memory block would be 3FFFh? since Y0 controls 0000h to 3FFFh then Y1 would be 4000h to 7FFFh etc?
A0—|
A1—|
A2—|
A3—|
A4—|
A5—|
A6—|
A7—|
A8—| All of these connect directly to address pins on each memory block
A9—|
A10-|
A11-|
A12-|
A13-|
_______
|74LS138|
| Y0|o------To CS/CE on memory block 0
A14----|A Y1|o------To CS/CE on memory block 1
A15----|B Y2|o------To CS/CE on memory block 2
GRND–|C Y3|o------To CS/CE on memory block 3
GRND–|G2A Y4|o
GRND–|G2B Y5|o
VCC—|G1 Y6|o
| Y7|o
|______|