FabiaTech FX5503, User Manual

Page: 56 / 62

FabIATech Corporation
51
Serial Ports
The ACEs (Asynchronous Communication Elements ACE1 to ACE2) 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, one and half (five-bit format only) or two stop bits. 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 to
handle 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)
Receiver Buffer Register (RBR)
Bit 0-7: Received data byte (Read Only)
Transmitter Holding Register (THR)
Bit 0-7: Transmitter holding data byte (Write Only)
Interrupt Enable Register (IER)
Bit 0: Enable Received Data Available Interrupt (ERBFI)