port 61h

Here is a little info about port 61h usage.

Straiph.

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

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.

pushall
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
cli
mov al,20h
out 20h,al ; send eoi to interrupt controller
popall
iret

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
byte.

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

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
buffer.

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.

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Port 61H: PS/2 System Control Port B
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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

0000:0000:0000:0000h
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!

what's your source if I may ask? Regards,
Bert Vingerhoets
vingerhoetsbert@hotmail.com
Don't worry what people think about you. They're too busy wondering what you think about them.

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

the page address is:


Straiph
0000:0000:0000:0000h
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!

i could be a little out of date! LOL 0000:0000:0000:0000h
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!