DIGITAL-LOGIC Microspace MSM586SEN Technical User Manual page 178

DIGITAL-LOGIC AG
I/O Ad- Read/Write
dress Status
03F8h R / W
03F9h R / W
03F9h R / W
03FAh R
03FBh R / W
03FCh R / W
Description
Baud rate divisor (low byte) - This byte along with the high
byte (03F9h) store the data transmission rate divisor.
bits 7-0 = Data bits 0-7 when the Divisor Latch Access
Bit (DLAB) is 1
Baud rate divisor (high byte) - This byte along with the low
byte (03F8h) store the data transmission rate divisor.
bits 7-0 = Bits 8-15 when DLAB = 1
Interrupt enable register
bits 7-4 = Reserved
bit 3 = 1 Modem status interrupt enable
bit 2 = 1 Receiver line status interrupt enable
bit 1 = 1 Transmitter holding register empty inter-
rupt
enable
bit 0 = 1 Received data available interrupt enable
Interrupt identification register - serial port 1
bits 7-3 = Reserved
bits 2-1 = Identify interrupt with highest priority
00 Modem status interrupt (4th priority)
01 Transmitter holding register empty (3rd
10 Received data available (2nd priority)
11 Receiver line status interrupt (1st
bit 0 = 0 Interrupt pending (
vice routine)
1 No interrupt pending
Line control register - serial port 1
bit 7 = Divisor Latch Access (DLAB)
0 Access receiver buffer, transmitter hold-
ing register, and interrupt enable register
1 Access divisor latch
bit 6 = 1 Set break enable. Forces serial output
to
there
bit 5 = Stick parity
bit 4 = Even parity select
bit 3 = Parity enable
bit 2 = Number of stop bits
bit 1 = Word length
00 5-bit word length
01 6-bit word length
10 7-bit word length
11 8-bit word length
Modem control register - serial port 1
bits 7-5 = Reserved
bit 4 = 1 Loopback mode for diagnostic testing of
bit 3 = 1 User-defined output 2
bit 2 = 1 User-defined output 1
bit 1 = Force Request To Send active
bit 0 = Force Data Terminal Ready active
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MSM586SEN/SEV Manual V1.5E
when DLAB = 0
priority)
priority)
register contents can be
used as a pointer to interrupt ser-
spacing state and remains
serial port.
Continued...