Datasheet

MCP2003/4
DS22230A-page 4  2010 Microchip Technology Inc.
1.3 Modes of Operation
For an overview of all operational modes, refer to
Table 1-1.
1.3.1 POWER-DOWN MODE
In Power Down mode, the transmitter and VREN are
both off. Only the receiver section and the wake-up
circuits are operational. This is the lowest power
mode.
On bus activity (e.g. a BREAK character), CS going to
a high level, or on a falling edge on WAKE, the device
will immediately enter Ready mode. If CS is held high
as the device transitions from Power Down to Ready
mode, the device will transition to Operation mode as
soon as internal voltages stabilize.
1.3.2 READY MODE
Upon entering the Ready mode, VREN is enabled and
the receiver detect circuit is powered up. The transmit-
ter remains disabled and the device is ready to receive
data but not to transmit.
Upon VBB supply pin power-on, the device will remain
in Ready mode as long as CS is low. If CS transitions
high, the device will enter Operation mode. However, if
the T
XD pin is held low when CS goes high, the device
will transition to Transmitter Off mode instead of
Operation mode.
1.3.3 OPERATION MODE
In this mode, all internal modules are operational.
The MCP2003/4 will go into the Power Down mode on
the falling edge of CS. The MCP2003/4 will enter
Transmitter Off mode in the event of a Fault condition.
These include: thermal overload, bus contention and
T
XD timer expiration.
The MCP2004 device can also enter Transmitter Off
mode if the FAULT
/TXE pin is pulled low
1.3.4 TRANSMITTER OFF MODE
Transmitter Off mode is reached whenever the
transmitter is disabled either due to a Fault condition or
pulling the nFAULT/TXE pin low on the MCP2004. The
fault conditions include: thermal overload, bus
contention or TXD timer expiration.
The MCP2003/4 will go into Power Down mode on
falling edge of CS, or return to Operation mode if all
faults are resolved and the FAULT
/TXE pin on the
MCP2004 is high.
FIGURE 1-2: OPERATIONAL MODES STATE DIAGRAM – MCP2003
Note: Bus activity is defined as LBUS dropping
below V
IL(LBUS) for longer than the Bus
Activity Debounce time (tBDB).
Operation
Mode
VREN ON
RX ON
TX ON
Ready
Mode
VREN ON
RX ON
TX OFF
TOFF
Mode
VREN ON
RX ON
TX OFF
Sleep Mode
VREN OFF
RX OFF
TX OFF
VBB > 5.5V
CS = 1 and TXD =0
CS=0
CS = 1 and TXD = 1
CS=0
Falling edge
on LIN
or CS = 1
CS = 1 and
TXD = 1
and No Fault
Fault
(
Thermal or Timer
)
POR
VREN OFF
RX OFF
TX OFF