FSK Modem and DTMF Codec
CMX865
5.10.2 General Control Register
General Control Register: 16-bit write-only. C-BUS address $E0
This register controls general features of the CMX865 such as the Powersave and Loopback modes, the
IRQ mask bits and the Relay Drive output. It also allows the fixed compromise equalisers in the Tx and Rx
signal paths to be disabled if desired, and sets the internal clock dividers to use either a 11.0592 or a
12.288 MHz XTAL frequency.
All bits of this register are cleared to 0 by a General Reset command.
15
0
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Bit:
TXA TXAN Xtal
off off freq
LB
Equ
Rly
drv
Pwr
Rst
Irqn
en
IRQ Mask Bits
General Control Register b15: Reserved, set to 0
General Control Register b14: Disconnect TXA Output
This bit allows the TXA output to be disconnected and set to high impedance.
b14 = 1
b14 = 0
TXA output disconnected.
TXA output connected (normal modem operation).
General Control Register b13: Disconnect TXAN Output
This bit allows the TXAN output to be disconnected and set to high impedance.
b13 = 1
b13 = 0
TXAN output disconnected.
TXAN output connected (normal modem operation).
General Control Register b12: Xtal Frequency
This bit should be set according to the Xtal frequency.
b12 = 1
b12 = 0
11.0592MHz
12.2880MHz
General Control Register b11: Analogue Loopback Test Mode
This bit controls the analogue loopback test mode. Note that in loopback test mode both Transmit
and Receive Mode Registers should be set to the same modem type and band or bit rate.
b11 = 1
b11 = 0
Local analogue loopback mode enabled
No loopback (normal modem operation)
General Control Register b10: Tx and Rx Fixed Compromise Equalisers
This bit allows the Tx and Rx fixed compromise equalisers in the modem transmit and receive
filter blocks to be disabled.
b10 = 1
b10 = 0
Disable equalisers
Enable equalisers (1200bps modem modes)
General Control Register b9: Relay Drive
This bit directly controls the RDRVN output pin.
b9 = 1
b9 = 0
RDRVN output pin pulled to VSS
RDRVN output pin pulled to VDD
© 2005 CML Microsystems Plc
18
D/865/3
CMLMICRO [ CML MICROCIRCUITS ]
