CMX867D2 CML Microcircuits, CMX867D2 Datasheet - Page 20

• Manufacturer Part Number: CMX867D2
• Description: Low power V.22 modem
• Manufacturer: CML Microcircuits

Low Power V.22 Modem
2001 Consumer Microcircuits Limited
General Control Register b8: Powerup
This bit controls the internal power supply to most of the internal circuits, including the Xtal
oscillator and V
device into Powersave mode.
When the power is first applied to the device, the following powerup procedure should be
followed to ensure correct operation.
When the device is switched from Powersave mode to normal operation by setting the
Powerup bit to 1, the Reset bit should also be set to 1 and should be held at 1 for about 20ms
while the internal circuits, Xtal oscillator and V
or receiver.
General Control Register b7: Reset
Setting this bit to 1 resets the CMX867’s internal circuitry, clearing all bits of the Transmit and
Receive Mode Registers and b15 and b13-0 of the Status Register.
General Control Register b6: IRQNEN (IRQN O/P Enable)
Setting this bit to 1 enables the IRQN output pin.
General Control Register b5-0: IRQ Mask bits
These bits affect the operation of the IRQ bit of the Status Register as described in section
1.5.10.7
i.
ii.
iii.
iv.
b8 = 1
b8 = 0
b7 = 1
b7 = 0
b6 = 1
b6 = 0
(Power is applied to the device)
Issue a General Reset command
Write to the General Control Register (address $E0) setting both the Powerup bit
(b8) and the Reset bit (b7) to 1 – leave in this state for a minimum of about 20ms –
it is required that the crystal initially runs for this time in order to clock the internal
logic into a defined state. The device is now powered up, with the crystal and V
supply operating, but is otherwise not running any transmit or receive functions.
The device is now ready to be programmed as and when required. Examples:
BIAS
A General Reset command could be issued to clear all the registers and
therefore powersave the device.
The Reset bit in the General Control Register could be set to 0 as part of a
routine to program all the relevant registers for setting up a particular operating
mode.
supply. Note that the General Reset command clears this bit, putting the
Device powered up normally
Powersave mode (all circuits except Ring Detect, RDRVN and C-BUS
interface disabled)
Internal circuitry in a reset condition.
Normal operation
IRQN pin driven low (to V
IRQN pin disabled (high impedance)
20
BIAS
stabilise before starting to use the transmitter
SS
) if the IRQ bit of the Status Register = 1
CMX867
D/867/2
BIAS