AP512 ACROPACK
USER
’S MANUAL
Acromag, Inc. Tel: 248-295-0310
- 32 - http://www.acromag.com
- 32 -
https://www.acromag.com
6
RI - NOT SUPPORTED
7
DCD - NOT SUPPORTED
An Asterisk (*) is used to indicate an active-low signal.
Note that reading MSR clears the delta-modem status indication (bit 0), but
has no effect on the bit-4 status bit. For both the LSR & MSR, the setting of
the status bits during a status register read operation is inhibited (the status
bit will not be set until the trailing edge of the read). However, if the same
status condition occurs during a read operation, that status bit is cleared on
the trailing edge of the read instead of being set again.
Note that not all UART signal paths are used by the AP512 models and their
corresponding UART pins are tied high (+5V). This includes, RI (Ring
Indicator), DSR (Data Set Ready), and DCD (Data Carrier Detect).
A power-up or system reset sets MSR bit-
0 to “0” (bit 4 is determined by the
corresponding input signal). All other bits are not used.
3.2.12 SCR - Scratch Pad (Read/Write)
This 8-bit read/write register has no effect on the operation of either serial
channel. It is provided as an aide to the programmer to temporarily hold
data.
3.2.13 Enhanced Register Set
The UART maintains compatibility with the industry standard 16C554/654
and 68C554/654 UARTs and provides new features to enhance serial
communication operation.
The new features provided by the UART are summarized in the following
register descriptions and includes software flow control via Xon and Xoff.
The Enhanced Register Set includes the following registers.
•
Enhanced Feature Register (EFR)
•
Xon-1, Xon-2
•
Xoff-1, Xoff-2
3.2.14 EFR - Enhanced Feature Register (Read/Write)
The Enhanced Feature register is used to enable or disable enhanced
features, including software flow control. This register is also used to unlock
access to programming the extended register functionality of IER bits 4-7,
ISR bits 4-5, FCR bits 4-5, and MCR bits 5-7.
Table 3.13 EFR - Enhanced
Feature Register
EFR
Bit
FUNCTION PROGRAMMING
