AP522 ACROPACK
USER
’S MANUAL
Acromag, Inc. Tel: 248-295-0310
- 39 - http://www.acromag.com
- 39 -
www.acromag.com
Transmitter Holding Register (THR), or the Interrupt Enable Register (IER). A
power-up or system reset sets all LCR bits to 0.
3.4.8 Modem Control Register (MCR)
–
Read/Write
The Modem Control register controls the interface with the modem or data
set as described below.
For model AP522, RTS is used to enable the transceiver to enable output of
TxD. The four modem control inputs (CTS, DSR, DCD, and RI) are
disconnected from their receiver input paths. In addition, the four modem
control outputs (DTR, RTS, OUT1, and OUT2) do not have transmitter output
paths.
Table 3.16 Modem Control
Register
MCR
Bit
FUNCTION
PROGRAMMING
0
Data Terminal
Ready Output
Signal (DTR)
0= DTR* Not Asserted (Inactive)
1= DTR* Asserted (Active)
1
Ready to Send
Output Signal
(RTS)
0 = RTS* Not Asserted (Inactive)
1 = RTS* Asserted (Active)
2
DTR# or RTS#
for Auto Flow
Control
0 = Uses RTS# and CTS# pins for auto
hardware flow control.
1 = Uses DTR# and DSR# for auto hardware
flow control.
3
Send Char
Immediate
0 = Send char immediate disabled (default).
1 = Send char immediate enabled.
4
Loop-back
0 = Loop-back Disabled
1 = Loop-back Enabled
5
1
Xon Control
0 = Disable Xon
1 = Enable any Xon function. In this mode
any RX character received will enable Xon.
6
1
Not Used
Must be logic 0
7
1
Divide by Four
0 = Divide by one. The internal 125MHz clock
is fed directly to the Programmable Baud
Rate Generator without further modification.
1 = Divide by four. 125MHz divided by 4, or
31.25MHz, is fed to the Programmable Baud
