
W83977EF/ CTF
PRELIMINARY
Publication Release Date: March 1999
-121 -
Revision A1
Bit 2: FDCPME. FDC auto power management enable.
= 0
disable the auto power management functions.
= 1
enable the auto power management functions.
Bit 1: URAPME. UART A auto power management enable.
= 0
disable the auto power management functions.
= 1
enable the auto power management functions.
Bit 0: URBPME. UART B auto power management enable.
= 0
disable the auto power management functions.
= 1
enable the auto power management functions.
CRF1 (Default 0x00)
Bit 7: WAK_STS. This bit is set when the chip is in the sleeping state and an enabled resume
event occurs. Upon setting this bit, the sleeping/working state machine will transition the
system to the working state. This bit is only set by hardware, and is cleared by writing a 1 to
this bit position, or by the sleeping/working state machine automatically when the global
standby timer expires.
= 0 the chip is in the sleeping state.
= 1 the chip is in the working state.
Bit 6: Device's trap status.
Bit 5 - 4: Reserved. Return zero when read.
Bit 3 - 0: Devices' trap status.
These bits of trap status indicate that the individual device Wakes-Up due to any I/O access,
IRQ, and external input to the device. The device's idle timer reloads the preset expiry
depending on which device wakes up. These 5 bits are controlled by the UART C, printer
port, FDC, UART A and UART B power down machines respectively . Writing a 1 clears this
bit and writing a 0 has no effect. Note that: the user is not supposed to change the status
while power management function is enabled.
Bit 6: URCTRAPSTS. UART C trap status.
= 0
UART C is now in the sleeping state.
= 1
UART C is now in the working state due to any UART C access, any IRQ, the
receiver begins receiving a start bit, the transmitter shift register begins transmitting a
start bit, or any transition on MODEM control input lines.
Bit 3: PRTTRAPSTS. Printer port trap status.
= 0
the printer port is now in the sleeping state.
= 1
the printer port is now in the workinging state due to any printer port access, any IRQ,
any DMA acknowledge, or any transition on BUSY, ACK#, PE, SLCT, and ERR#
pins.