Low Power V.32 bis Modem
CMX869
6.1
General Reset Command
General Reset Command
(no data)
C-BUS address $01
This command resets the device and clears all bits of the General Control, Transmit Mode and Receive
Mode Registers and bits 15 and 13-0 of the Status Register. The General Reset command places the
device into Powersave mode.
Whenever power is applied to the CMX869, a built in power-on-reset circuit ensures that the device
powers up into the same state as follows a General Reset command. Nevertheless it is recommended that
a General Reset command be sent to the device on power-up, after which the General Control Register
should be set as required.
6.2
General Control Register
General Control Register: 16-bit write-only. C-BUS address $E0
This register controls general features of the CMX869 such as the Powersave and Loopback modes, the
IRQ mask bits and the Relay Drive output.
All bits of this register are cleared to 0 by a General Reset command.
15
0
14
13
0
12
0
11
LB
10
9
8
7
6
5
4
3
2
1
0
Bit:
Hi
Gain
2C
Rly
drv
Pwr
Rst
Irqn
en
IRQ Mask Bits
General Control Register b15: Reserved, set to 0
General Control Register b14: Select high input gain
This bit selects the RXBN input pin and is used to increase the input stage gain.
B14 = 1
B14 = 0
RXBN internally connected to RXAN
RXBN open circuit
General Control Register b13,12: Reserved, set to 00
General Control Register b11: Analogue Loopback test mode
This bit controls the analogue loopback test mode. In loopback test mode both Transmit and
Receive Mode Registers should be set to the same modem type, band and bit rate. The line
interface relay must be open, as the test transmission that is fed back into the Rx path will
appear at the Tx pins. Analogue loopback is not available in QAM modem modes.
b11 = 1
b11 = 0
Local analogue loopback mode enabled
No loopback (normal modem operation)
General Control Register b10: Modem 2-Character mode
Selects whether the Tx Data and Rx Data Registers operate in 1 or 2 character mode.
b10 = 1
b10 = 0
2 character mode
1 character mode
The character mode is only updated on exit from General Control initated reset, so General
Control Register b7 must be set (written = 1) then cleared (written = 0), in conjunction with setting
the desired character mode.
© 2004 CML Microsystems Plc
20
D/869/4
CMLMICRO [ CML MICROCIRCUITS ]
