CONFIGURATION SEQUENCE
Exit Configuration Mode
To program the configuration registers, the
following sequence must be followed:
1. Enter Configuration Mode
To exit the Configuration State the system writes
0xAA to the CONFIG PORT. The chip returns
to the RUN State.
2. Configure the Configuration Registers
3. Exit Configuration Mode.
Note: Only two states are defined (Run and
Configuration). In the Run State the chip will
always be ready to enter the Configuration
State.
Enter Configuration Mode
To place the chip into the Configuration State
the Config Key is sent to the chip's CONFIG
PORT. The config key consists of 0x55 written
to the CONFIG PORT. Once the configuration
key is received correctly the chip enters into the
Configuration State (The auto Config ports are
enabled).
Programming Example
The following is an example of a configuration
program in Intel 8086 assembly language.
;----------------------------.
; ENTER CONFIGURATION MODE
|
;----------------------------'
MOV
MOV
OUT
DX,3F0H
AX,055H
DX,AL
Configuration Mode
The system sets the logical device information
and activates desired logical devices through
the INDEX and DATA ports. In configuration
mode, the INDEX PORT is located at the
CONFIG PORT address and the DATA PORT is
at INDEX PORT address + 1.
;----------------------------.
; CONFIGURE REGISTER CRE0,
; LOGICAL DEVICE 8
;----------------------------'
|
|
MOV
MOV
OUT
Reg
MOV
MOV
OUT
;
MOV
MOV
OUT
MOV
MOV
OUT
DX,3F0H
AL,07H
DX,AL ;Point to LD# Config
The desired configuration registers are accessed
in two steps:
DX,3F1H
AL, 08H
a. Write the index of the Logical Device
Number Configuration Register (i.e., 0x07) to
the INDEX PORT and then write the number
of the desired logical device to the DATA
PORT
b. Write the address of the desired
configuration register within the logical
device to the INDEX PORT and then write or
read the configuration register through the
DATA PORT.
DX,AL;Point to Logical Device 8
DX,3F0H
AL,E0H
DX,AL ; Point to CRE0
DX,3F1H
AL,02H
DX,AL ; Update CRE0
;-----------------------------.
; EXIT CONFIGURATION MODE
|
;-----------------------------'
Note: If accessing the Global Configuration
Registers, step (a) is not required.
MOV
MOV
OUT
DX,3F0H
AX,0AAH
DX,AL
132
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