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Students Click Here

port 61h

port 61h

port 61h

what is port 61h?
what it return?
and more info if u can


RE: port 61h

Here is a little info about port 61h usage.


Ports 60H-63H: PC 8255 Parallel    I/O Port Chip for Keyboard and Status
Ports 60H-64H: PS/2 Intel 8042 Keyboard/Auxiliary Device Controller

The 8255 Parallel Port Controller and Programmable Peripheral Interface

The 8255 chips control parallel    ports on the PC    system,    and acts as the
Programmable Peripheral    Interface (PPI)    for the    CPU, occupying four
consecutive port addresses 060H-063H.  The PPI can control three
independent ports (A, B, and C)    as either input    or output.  The    fourth
port address is    used as    a control port for the chip.  The following
shows the meaning of a control byte sent to the    write-only control port:

     bit              Value         Action

       7   Mode Set    Flag          0     Inactive   1  Active
     6,5   Mode Selection A         00     Mode 0       01  Mode 1    1x  Mode 2
       4   Port A              0     Output        1  Input
       3   Port C (upper 4 bits)  0     Output        1  Input
       2   Mode Selection B          0     Mode 0        1  Mode 1
       1   Port B              0     Output        1  Input
       0   Port C (lower 4 bits)  0     Output        1  Input

If bit 7 is 0, the byte    sent is    used to    set or reset a bit in port C.
Mode 1 uses three port C lines for handshaking and interrupt control of
port A.     For input, if PC4=0, port A latches data and PC5 goes high to
indicate 'buffer full' for device connected to input lines.  PC5 returns
low when the CPU reads port A.    If port    A interrupts are enabled, PC3
also goes high when a byte is received,    which can be used for an IRn
line to    an 8259A interrupt controller.    Port B functions like port A in
mode 1 except it uses the three    low bits of port C for control.     Output
in mode    1 is similar.  Mode 2 allows port A to operated    bidirectionally,
with handshaking and interrupt control using five bits of port C.

The PPI    Status Ports on    the IBM    PC compatibles at port addresses 060H to
062H perform the following functions (all set to mode 0, A made    input, B
output,    C input    by sending 099H    to 063H):

060H Port A Input (acts    as a one byte device output register):

    If PB7 = 0 Read    Keyboard Scan Code

    If PB7 = 1 Read    switches
           PA7,6   = SW1-8,7  # of drives
           PA5,4   = SW1-6,5  monitor type
                   11 = monochrome
                   10 = 80x25 color
                   01 = 40x25 color
           PA3,2,0 = SW1-4,3,1 Reserved
           PA1     = SW3       Math    chip mounted

061H Port B Output (acts as a one byte device control register):

           PB7 0 enable keyboard read
           1 clear keyboard and    enable sense of    SW1
           PB6 0 hold keyboard clock low, no shift reg. shifts
           1 enable keyboard clock signal
           PB5 0 enable i/o    check
           1 disable i/o check
           PB4 0 enable r/w    memory parity check
           1 disable r/w parity    check
           PB3 0 turn off LED
           1 turn on LED (old cassettee    motor off)
           PB2 0 read spare    key
           1 read r/w memory size (from    Port C)
           PB1 0 turn off speaker
           1 enable speaker data
           PB0 0 turn off timer 2
           1 turn on timer 2, gate speaker with    square wave

062H Port C Input (acts    as a one byte device output register):
        (Set PB2 (PC) or PB3 (XT) first.)

           PC7 0 no    parity error or    PB4=1
           1 r/w memory    parity check error
           PC6 0 no    i/o channel error or PB5=1
           1 i/o channel check error
           PC5 0 timer 2 output 0
           1 timer 2 output 1
           PC4   reserved (old cassettee data input)
           PC3,2,1,0 = r/w memory (SW2-4,3,2,1) if PB2=1
             =  spare key (SW2-8,7,6,5) if PB2=0

       PC7 and PC6 are used by the NMI handler to tell whether RAM parity
       error, i/o channel status error,    or, if both are    0, an 8087 error

Example: Direct    reading    of PC keyboard scan code (replacement for INT 09):

 1. Read scan code.  Note that "make" key scan code has    bit 7=1,
    "break" code has bit 7=0, except on    AT, for    which bit 7 is always 0,
    a "break" produces a 0F0H code, then the key scan code.
 2. Send acknowledge to    keyboard by toggling bit 7 to 1, then back to 0.
 3. Put    keyboard in buffer.
 4. Signal EOI to the interrupt    controller.

       in al,060h     ;    get key    code
       push ax          ;    save it
       in al,061h     ;    get current control
       mov ah,al      ;    save PB    control
       or al,80h      ;    set keyboard bit
       out 061h,al    ;    keyboard acknowledge
       xchg ah,al     ;    get back PB
       out 061h,al    ;    reset PB control
       pop ax          ;    get back code
       ...          ;    save code in buffer
       mov al,20h
       out 20h,al     ;    send eoi to interrupt controller

The PS/2 8042 Keyboard/Auxiliary Device    Controller

On the PS/2, an    Intel 8042 chip    replaces the 8255, using ports 60H and
64H. Port 61H serves as    a system control port for compatibility    with the
PC. The    8042 controls both the keyboard    and an auxiliary device, such as
a mouse. It receives serial data, check    parity,    translates keyboard scan
codes, and presents data at the    data port 60H.    The interface can
interrupt the system (IRQ1) or can wait    for polling.  The I/O port 64H
is the command/status port. A read gives status, a write is interpreted
as a command.  The 8042    provides for a password    security mechanism.

A read from port 64H gives the following status    byte:

   Bit       Function
    7       1 = Parity error
    6       1 = General Time Out
    5       1 = Auxiliary output    buffer full
    4       1 = Inhibit switch
    3       1 = Command/data
    2       1 = System flag
    1       1 = Input buffer full
    0       1 = Output buffer full

The status register can    be read    at any time.  The data port 60H    should
be read    only when the output buffer full bit in    the status register is
1. Data    should be written to the 8042 input buffer only    when the input
buffer full bit    in the status register is 0.  If the auxiliary output
buffer full bit    is 1, then the data read came from the auxiliary device.
The command port 64H should be written to only when the    status register
input buffer full bit and the output buffer full bit are 0.  Devices
connected to the 8042 should be    disabled before    sending    a command that
generates output.

The following are recognized commands sent to port 64H:

  20-3FH   Read    the 8042 RAM - Bits D5-D0 specify the address.
           Address 0 is the    current    command    byte.

  60-7FH   Write to the    8042 RAM   - Bits D5-D0    specify    the address.
           Address 0 will mean the next byte of data out at    port 60H
           is the command byte, defined using:

          Bit     Function
           7      Reserved = 0
           6      1    = IBM keyboard translate mode
           5      1    = Disable auxiliary device
           4      1    = Disable keyboard
           3      Reserved = 0
           2      1    = Place    system flag in status register
           1      1    = Enable auxiliary interrupt
           0      1    = Enable keyboard interrupt

    A4       Test    if password is installed.  Data    0FAH on    port 60H means
       that    the password is    installed, 0F1H    means that the password
       is not installed.

    A5       Load    Security - initiate the    password load procedure.  Following
       this    command    the 8042 will input from the data port until a
       null    is detected.

    A6       Enable Security - enable the    security feature, when the password
       pattern is currently    loaded.

    A7       Diable auxiliary device interface - set bit 5 of the    command

    A8       Enable auxiliary device interface - reset bit 5 of the command

    A9       Interface test - test the auxiliary device clock and    data lines.
       The result is placed    in the output buffer at    60H:

          Result      Meaning
        00      No error
        01      Aux. device clock line stuck low
        02      Aux. device clock line stuck high
        03      Aux. device data line    stuck low
        04      Aux. device data line    stuck high

    AA       Self    test - tests 8042.  A 55H is placed in output buffer if
       no errors are detected.

    AB       Interface test - cause the 8042 to test the keyboard    clock
       and data lines.  Result reported as in command A9.

    AC       Reserved

    AD       Disable keyboard interface -    set bit    4 of the command byte.

    AE       Enable keyboard interface - reset bit 4 of the command byte.

    C0       Read    input port - read the 8042 input port and put it in the
       output port.     If bit    3 is 0,    the fuse on the    +5 Vdc line
       on the system board to the keyboard is open.

    C1       Poll    input port low - put port 1 bits 0-3 in    status bits 4-7.

    C2       Poll    input port high    - put port 1 bits 4-7 in status    bits 4-7.

    D0       Read    output port - put data from output port    into the output

    D1       Write output    port - put next    byte written to    60H into the
       output port.     Caution:  Bit 0 of the    output port is connected
       to the System Reset line.  This bit should not be written low.

    D2       Write keyboard output buffer    - put next byte    written    to 60H
       into    output buffer and issue    device interrupt if enabled.
       This    produces a simulated keyboard output.

    D3       Write auxiliary device output buffer    - put next byte    written
       to 60H input    buffer in output buffer    as if initiated    by the
       auxiliary device and    issue interrupt    if enabled.

    D4       Write to auxiliary device - transmit    next byte written to 60H
       input buffer    to auxiliary device.

    E0       Read    test inputs - cause the    8042 to    read its T0 and    T1 inputs.
       This    data is    placed in the output buffer bits 0 and 1.

  F0-FF       Pulse output    port - pulse bits 0-3 of the 8042 output port
       for about 6 usec.  Bits 0 to    3 indicate which bits are to be
       pulsed.  A 0    indicates bit should be    pulsed.     Caution:
       Bit 0 of the    8042 output port is connected to the System Reset
       line.  Pulsing this bit resets the system microprocessor.

On the PS/2, the 8042 controller can pass commands to the keyboard
through    port 60H:

    ED       Set/reset status indicators.    Rresponse is ACK (0FAH), system
       acceptance of ACK requires system to    raise clock and    data lines
       for at least    500 usec.

    EE       Echo    test (valid response is    EE)

    EF       Invalid command

    F0       Select alternate scan codes (response is ACK, system    then sends
       option byte of 01, 02, or 03, response is ACK)

    F1       Invalid command

    F2       Read    keyboard ID (response is ACK plus two ID bytes of 83ABH)

    F3       Set typematic rate/delay (response is ACK, system sends rate/delay
       byte, response is ACK.  The rate/delay byte is:

          bit      function

           7       reserved    = 0
          6-5      (delay/250msec -    1)
          4-3      doubling    factor of rate
          2-0      (rate/(240/sec) - 8)

    F4       Enable (response is ACK, clears buffer, clears last typematic
       key,    and starts scanning).

    F5       Default disable (resets all conditions to power-on state, sends
       ACK,    stops scanning).

    F6       Set default (resets to power-on state, sends    ACK, sets default
       key types for scan code 3, continues    scanning).

  F7-FA       Set all keys    to typematic, make/break, make,    or typematic/make/
       break for scan code 3 (responds with    ACK).

  FB-FD       Set a key type to typematic,    make/break, or make (response is
       ACK,    then keyboard prepares to receive key scan code    from set 3.

    FE       Send    the previous output again.

    FF       Reset the keyboard and start    internal self-test. Response is
       ACK.     System    must acknowledge ACK by    raising    clock and data lines
       for over 500    usec.  Following acceptance of ACK, keyboard is
       reinitialized and performs a    Basic Assurance    Test (BAT).  The
       keyboard defaults to    scan code 2.

The PS/2 keyboard may send the following codes to the system:

    00       Key detection error/overrun under scan code 2 or 3.

   83AB       Keyboard ID bytes.

    AA       Basic Assurance Test    completed.

    FC       Basic Assurance Test    failed.

    EE       Echo    of EE command.

    FA       ACK code.

    FE       Resend. Invalid input or parity error.

    FF       Key detection error/overrun under scan code 1.

Port 61H: PS/2 System Control Port B

Write operations:

   Bit     Function

    7     Reset system timer 0 output latch (IRQ0)
    6     Reserved
    5     Reserved
    4     Reserved
    3     Enable    channel    check
    2     Enable    parity check
    1     Speaker data enable
    0     System    timer 2    gate to    speaker

Read operations:

    7     1 = Parity check occurred
    6     1 = Channel check occurred
    5     System    timer 2    output
    4     Toggles with each refresh request
    3     Enable    channel    check result
    2     Enable    parity check result
    1     Speaker data enable result
    0     System    timer 2    gate to    speaker    result

The people who have nothing to say and say it too loud have little knowledge, It's the quiet ones you need to worry about!

RE: port 61h

this is a web page that i found using www.google.com and searched using 'io port 61h'

the page address is:



The people who have nothing to say and say it too loud have little knowledge, It's the quiet ones you need to worry about!

RE: port 61h

i could be a little out of date!

The people who have nothing to say and say it too loud have little knowledge, It's the quiet ones you need to worry about!

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