Input Output

1
Input / Output

• AMS-505
• Serial 2.6

2
Review
3
Input / Output

• Purpose of I/O - to convert information from / to
  human usable form to / from CPU usable form.
• No I/O, no useful computer.
• Two types of I/O
• Serial and Parallel

4
General IO
5
Serial IO

• One bit at a time
• Slow transfer rates
• One signal path for Tx, one for Rx
• Interface circuits convert parallel to serial and
  vice-versa.
• Eg Shift registers

6
Serial Interface
Rx
Buffer
Data Bus
7
Serial Interface
Tx
Buffer
Data Bus
8
Serial - RS232-C

• Standardized 25 pin connector
• Modem connection
• UART
• parallel - to - serial conversion
• rates from 110 - 56 kbits / sec
• Pin 2 - Tx
• Pin 3 - Rx

9
RS232-C / Modem
phone line
RS232
RS232
modem
modem
10
USB

• 127 devices
• USB has dual-speed data transfer, 1.5Mbps and
  12Mbps
• Can provide limited power, maximum 500mA of
  current, to devices attached on the bus.
• CD recorders, hard drives, speakers, scanners,
  camcorders, DVD drives

11
Parallel IO

• Parallel data transfers involve multiple bits
  being moved at one time.
• Parallel data transfer is much faster than serial
  data transfer.
• Parallel transfers normally occur between devices
  that are physically close. (printer, hard drive)
• Parallel data need not come from another computer
  or peripheral device.

12
SCSI

• Small Computer Systems Interface
• In a SCSI environment, devices are daisy -
  chained together using a common cable.
• SCSI-1 5 Mbps 7 devices 8-bit bus
• SCSI-2 up to 40 Mbps 16 and 32 bit buses
• SCSI-3 20 Mbps 16-bit transfer

13
EPP

• Enhanced Parallel Port
• High performance parallel port link that is
  compatible with the standard parallel port.
• Intended for non-printer devices.
• 8-bit connectable ports
• 4 EPPs 32 bit words
• Transfer rates from 500K to 2M bytes per second

14
Memory Mapped IO

• Memory Map
• Addressable memory space
• eg 10 address lines 210 locations 1K
• 20 address lines 1M
• 21 address lines 2M
• 32 address lines ???
• IO interface registers addressable
• Configure, read, write, and check device status
  using memory-type instructions

15
Memory-Mapped IO
16
Next

• System Interconnect (Buses)