Formosa Industrial Computing MBM-530NS, User Manual

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-20- MBM-530NS User’s Manual
1.5 Serial Port
The ACEs (Asynchronous Communication Elements ACE1 to ACE4) are used
to convert parallel data to a serial format on the transmit side and convert
serial data to parallel on the receiver side. The serial format, in order of
transmission and reception, is a start bit, followed by five to eight data bits, a
parity bit (if programmed) and one, 1.5 (in a five-bit format only) or two stop
bits (in a 6,7, or 8-bit format). The ACEs are capable of handling divisors of 1
to 65535, and produce a 16x clock for driving the internal transmitter logic.
Provisions are also included to use this 16x clock to drive the receiver logic. Also
included in the ACE a completed MODEM control capability, and a processor
interrupt system that may be software tailored to the computing time required
handling the communications link.
The following table is a summary of each ACE accessible register.
DLAB
Port
Address
Register
Receiver buffer (read)
0 base + 0
Transmitter holding register (write)
0 base + 1 Interrupt enable
X base + 2 Interrupt identification (read only)
X base + 3 Line control
X base + 4 MODEM control
X base + 5 Line status
X base + 6 MODEM status
X base + 7 Scratched register
1 base + 0 Divisor latch (least significant byte)
1 base + 1 Divisor latch (most significant byte)
(1) Receiver Buffer Register (RBR)
Bit 0-7: Received data byte (Read Only)
(2) Transmitter Holding Register (THR)
Bit 0-7: Transmitter holding data byte (Write Only)