Advantech Carbon Monoxide Alarm PCI-1718 Series User Manual

The register at BASE+19H clears the FIFO buffer and sets its empty flag 
(EF). The FIFO status register, address BASE+19H, has flags which you 
can read to determine the current state of the FIFO buffer, including full 
flag, half-full flag, and empty flag.

EF  FIFO empty flag
1 

FIFO is empty

0 

FIFO is not empty

HF FIFO 

half-full 

flag

1 

FIFO is half-full or more than half-full

0 

FIFO is less than half-full

FF  FIFO full flag
1 

FIFO is full

0 

FIFO is not full

Writing any value to BASE+19H clears all data in the FIFO and sets the 
empty flag (EF) to 1.

Read

FIFO status

Bit  #

7

6

5

4

3

2

1

0

BASE + 19H

FF

HF

EF

Write

FIFO clear

Bit  #

7

6

5

4

3

2

1

0

BASE + 19H X

X

X

X

X

X

X

X