Acrosser AR-B9612 - Manual (Page 10)

AR-B9612 User’s Guide
2-5
2.5 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, 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 is a complete MODEM
control capability, and a processor interrupt system that may be
software tailored to the computing time required to handle the
communications link.
The follows is summary of each ACE accessible registers
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)
Table 2-3 ACE Accessible Register