1. Kanwaljeet Singh, Lovely Professional University.
Memory-Mapped I/O
9/21/2018

2. Memory mapped I/O interfacing
In memory- mapped I/O interfacing , the I/O devices are considered as a memory locations.
I/O devices are being identified by 16- address.
To transfer the data b/w MPU and I/O devices, memory related instructions(STA,LDA & etc) and Memory control signal(MEMR(AL) and MEMW(AL)) are used .
Kanwaljeet Singh, Lovely Professional University.
9/21/2018

3. If the o/p device is connected Instead of m/y register, the A-Reg
To understand the memory mapped I/O interfacing , we required to know how data byte is transferred from MPU to M/Y location and Vice-Versa..
Consider instruction to transfer the contents of A- reg to memory location 526Ah.
If the o/p device is connected
Instead of m/y register, the A-Reg
Contents will be transferred to
O/P device.
This technique is called as Memory- Mapped I/O
Kanwaljeet Singh, Lovely Professional University.
9/21/2018

4. Let us now Consider LDA instruction(I/O to MY) LDA 2001h
Consider this 2001 Is the address of i/p device specified by LDA
Memr and Memw control signal should be connected to I/O devices instead of IOR and IOW(AL)
Kanwaljeet Singh, Lovely Professional University.
9/21/2018

5. Kanwaljeet Singh, Lovely Professional University. 9/21/2018
Latch :
Kanwaljeet Singh, Lovely Professional University.
9/21/2018

6. Device selection and Data transfer in M/y-mapped I/O requires 3 steps
Decode the address bus to generate the address Pulse
AND the control signal with device address pulse and generate the device select(I/O select ) pulse
Use the device select pulse to enable the I/O port
Kanwaljeet Singh, Lovely Professional University.
9/21/2018

7. Read: LDA FFF9H; read the switches CMA; Compliment switch reading
STA FFF8H; Send the switch positions to output port and turn on/OFF appliances
JMP READ; goes back and read again
Kanwaljeet Singh, Lovely Professional University.
9/21/2018

8. comparision Device address is 8 bit Control signals IOR and IOW
Memory-mapped I/O
Peripheral I/O
Device address is 16 bit
Control signal MEMR and MEMW(AL)
Instructions (STA,LDA,MOV M,R)
Data transfer is between any register and I/O
More hardware is needed to decode 16-bit address
Device address is 8 bit
Control signals IOR and IOW
Instructions like IN and OUT is only is used
Data transfer is between I/O and accumulator
Less hardware is needed to decode 8 bit address.
Kanwaljeet Singh, Lovely Professional University.
9/21/2018