IMP16C554
transmitter are controlled separately either
one or both can in the polled mode operation
by utilizing the Line status Register.
A) LSR BIT-0 will be set as long as there is
one byte in the receive FIFO.
B) LSR BIT4-1 will specify which error(s) has
occurred.
C) LSR BIT-5 will indicate when the
transmit FIFO is empty.
D) LSR BIT-6 will indicate when both transmit
FIFO and transmit shift register are empty.
E) LSR BIT-6 will indicate when there are
any errors in the receive FIFO.
The IMP16C554 provides four level prioritized
interrupt conditions to minimize software
overhead during data character transfers. The
interrupt Status Register (ISR) provides the
source of the interrupt in prioritized matter.
During the read cycle the IMP16C554 provides
the highest interrupt level to be serviced by
CPU. No other interrupts are acknowledged
until the particular interrupt is serviced. The
following sre the prioritized interrupt levels:
Priority level
The MS16C554 requires to have two step FIFO
enable operation in order to enable receive trigger
levels.
P
1
D3
0
D2
1
C1
1
D0
0
Source
interrupt
of
the
LSR (Receiver Line
Status Register)
PROGRAMMABLE BAUD RATE
GENERATOR
2
0
1
0
0
RXRDY
Data Ready)
(Received
2*
3
1
1
0
0
RXRDY
Data time out)
TXRDY (Transmitter
Holding
Empty)
(Received
The IMP16C554 contains a programmable Baud
Rate Generator that is capable of taking any
clock input from DC-24 MHz and dividing it by
0
0
1
0
Register
any divisor from
1 to 216-1.The output
frequency of the Baud out* is equal to 16X of
transmission baud rate (Baudout*=16 x Baud
Rate). Customize Baud Rates can be
achieved by selecting proper divisor values for
MSB and LSB of baud rate generator.
4
0
0
0
0
MSR (Modem Status
Register)
*RECEIVE TIME-OUT:
This mode is enabled when the
UART is operating in FIFO mode. Receive
time out will not occur if the receive FIFO is
empty. The time out counter will be reset at
the center of each stop bit received or each
time out value is T (Time out length in bits)=4
INTERRUPT ENABLE REGISTER (IER)
The interrupt Enable Register (IER) masks the
incoming interrupts from receiver ready,
transmitter empty, line status and modem
status registers to the INT output pin.
IER BIR-0
0=disable the receiver ready interrupt.
1=enable the receiver ready interrupt.
IER BIR-1
X
P (Programmed word length)+12. To
convert time out value to a character value,
user has to divide this number to its complete
word length + parity (if used)+number of stop
bits and start bit.
0=disable the transmitter empty interrupt.
1=enable the transmitter empty interrupt.
IER BIR-2
0=disable the receiver line status interrupt.
1=enable the receiver line status interrupt.
IER BIR-3
Example-A: if user programs the word
length=7,and no parity and one stop bit. Time
out
length)+12=40 bits Character time =40 / 9
(programmed word length=7)+(stop
will
be:T=4x7(programmed
word
bit=1)+(start bi=1)=4.4 characters.
0=disable the modem status register interrupt.
1=enable the modem status register interrupt.
IER BIR7-4
Example-B: if user programs the word
length=7,with parity and one stop bit, the time
out will be: T=4x7 (programmed word
length)+12=40 bits Character time =40 / 10
(programmed word length=7) + (parity=1) +
All these bits are set to logic zero.
INTERRUPT STATUS REGISTER (ISR)
7
408-432-9100/www.impweb.com
© 2002 IMP, Inc.
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