AP500/AP520/AP521 ACROPACK
USER
’S MANUAL
Acromag, Inc. Tel: 248-295-0310
- 37 - http://www.acromag.com
- 37 -
www.acromag.com
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
3-0
Software
Flow
Control
00XX = No Transmit Flow Control
10XX = Transmit Xon1/Xoff1
01XX = Transmit Xon2/Xoff2
11XX = Transmit Xon1 and Xon2, Xoff1 and Xoff2
XX00 = No receive Flow Control
XX10 = Receiver Compares Xon1/Xoff1
XX01 = Receiver Compares Xon2/Xoff2
1011 = Transmit Xon1/Xoff1, Receiver compares
Xon1 or Xon2, Xoff1 or Xoff2.
0111 = Transmit Xon2/Xoff2. Receiver compares
Xon1 or Xon2, Xoff1 or Xoff2.
1111 = Transmit Xon1 and Xon2, Xoff1 and Xoff2;
Receiver compares Xon1 and Xon2, Xoff1
