Data bus

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Quick Questions

Shade in the A or B circle for each question.

1. The data bus carries data and instructions between the CPU and RAM.

A True

B False

2. Which direction can the data bus carry signals?

A Both directions (two-way)

B One direction only (CPU to RAM)

3. Which register does the data bus connect to in the CPU?

A Memory address register (MAR)

B Memory data register (MDR)

4. The data bus carries only data and never instructions.

A False

B True

5. Which bus carries the instruction from RAM to the CPU during the fetch stage?

A Address bus

B Data bus

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1data bus		ARAM --data bus--> MDR (instruction)
2MDR <-> Data bus <-> RAM		BThe data bus carries instructions as well as data. Instructions are fetched from RAM along it into the MDR.
3The data bus carries instructions as well as data, so a fetched instruction travels along it from RAM to the CPU		CThe data bus works in both directions: the MDR can send data to RAM or receive data from RAM
4The data bus is two-way, so the CPU can both read from RAM and write to RAM		DA set of wires that carries data and instructions between the CPU and RAM
5The data bus carries only data, never instructions		EThe data bus is two-way (bidirectional). It carries values from RAM to the CPU and from the CPU to RAM. Only the address bus is one-way.
6The data bus is one-way: CPU -> RAM only		FRead: RAM -> MDR \| Write: MDR -> RAM

Definitions

data bus

Fill in the Blanks

Complete each line of code by filling in the missing parts.

The data ___ links the CPU and RAM

Data bus: _______ between CPU and RAM

Data bus carries data and ____________

RAM -> data bus -> ___

Writing: MDR -> ____ bus -> RAM

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A PC -> MAR via address bus

B RAM finds the address

C Data bus carries instruction

D Data bus -> MAR

Question 2

A bus <- 'data bus'

B directions <- 1

C joins <- 'CPU and RAM'

Question 3

A DATA BUS: one-way

B Links CPU and RAM

C Carries data and instructions

D Connects to the MDR

Question 4

A CPU stores a result in RAM

B Result is in the MDR

C Data bus: RAM -> CPU

D RAM saves the value

Question 5

A IF reading from RAM THEN

B data bus: RAM -> CPU

C ELSE

D data bus: not used

Answer Key

Data bus

Section A: Quick Questions

A — True

A — Both directions (two-way)

B — Memory data register (MDR)

A — False

B — Data bus

Section B: Match the Pairs

data bus → A set of wires that carries data and instructions between the CPU and RAM

MDR <-> Data bus <-> RAM → The data bus works in both directions: the MDR can send data to RAM or receive data from RAM

The data bus carries instructions as well as data, so a fetched instruction travels along it from RAM to the CPU → RAM --data bus--> MDR (instruction)

The data bus is two-way, so the CPU can both read from RAM and write to RAM → Read: RAM -> MDR | Write: MDR -> RAM

The data bus carries only data, never instructions → The data bus carries instructions as well as data. Instructions are fetched from RAM along it into the MDR.

The data bus is one-way: CPU -> RAM only → The data bus is two-way (bidirectional). It carries values from RAM to the CPU and from the CPU to RAM. Only the address bus is one-way.

Section C: Definitions

data bus — A set of wires that carries data and instructions in both directions between the CPU and RAM. It connects to the MDR.

Section D: Fill in the Blanks

The data bus links the CPU and RAM

Data bus: two-way between CPU and RAM

Data bus carries data and instructions

RAM -> data bus -> MDR

Writing: MDR -> data bus -> RAM

Section E: Spot the Error

D — The data bus connects to the MDR, not the MAR. The MAR holds addresses and uses the address bus. The line should be Data bus -> MDR.

B — The data bus is two-way. Data and instructions travel in both directions between the CPU and RAM, so directions should be 2.

A — The data bus is two-way (bidirectional), not one-way. It should read DATA BUS: two-way.

C — When the CPU writes a result to RAM, the data bus carries it from the CPU to RAM. The line should be Data bus: CPU -> RAM.

D — The data bus is used for both reading and writing because it is two-way. When writing, it should be data bus: CPU -> RAM.