FDC37C78-HT Datasheet, PDF (62/82 Pages) Microchip Technology – Floppy Disk Controller

CONFIGURATION
The configuration of the chip is programmable
through software selectable configuration
registers.
CONFIGURATION REGISTER ADDRESS
The Configuration Registers are located at
address offset +0 and +1 with nCS active.
CONFIGURATION REGISTERS
The configuration registers are used to select
programmable options of the chip. After power up,
the chip is in the default mode. The default modes
are identified in the Configuration Mode Register
Description. To program the configuration
registers, the following sequence must be
followed:
1.
Enter Configuration Mode.
2.
Configure the Configuration Registers.
3.
Exit Configuration Mode.
Enter Configuration Mode
To enter the configuration mode, two writes in
succession to port +0 with 55H data are required.
If a write to another address or port occurs
between these two writes, the chip does not enter
the configuration mode. It is strongly
recommended that interrupts be disabled for the
duration of these two writes.
Configuration Mode
The chip contains configuration registers CR00-
CR1F. These registers are accessed by first
writing the number (0-1FH) of the desired register
to port +0 and then writing or reading the
configuration register through port +1.
Exit Configuration Mode
The configuration mode is exited by writing an
AAH to port +0.
Programming Example
The following is an example of a configuration
program in Intel 8086 assembly language and
assumes that the base address is set to 3F0H.
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