5−9
5.5 ExCA Card Status-Change Register
The ExCA card status-change register controls interrupt routing for I/O interrupts as well as other critical 16-bit PC
Card functions. The register enables these interrupt sources to generate an interrupt to the host. When the interrupt
source is disabled, the corresponding bit in this register always reads 0b. When an interrupt source is enabled, the
corresponding bit in this register is set to indicate that the interrupt source is active. After generating the interrupt to
the host, the interrupt service routine must read this register to determine the source of the interrupt. The interrupt
service routine is responsible for resetting the bits in this register as well. Resetting a bit is accomplished by one of
two methods: a read of this register or an explicit write back of 1b to the status bit. The choice of these two methods
is based on bit 2 (interrupt flag clear mode select) in the ExCA global control register (ExCA offset 1E/5E/81E, see
Section 5.20). See Table 5−7 for a complete description of the register contents.
Bit 7 6 5 4 3 2 1 0
Default 0 0 0 0 0 0 0 0
Register: ExCA card status-change
Offset: CardBus socket address + 804h; ExCA offset 04h
Type: Read-only
Default: 00h
Table 5−7. ExCA Card Status-Change Register Description
BIT SIGNAL TYPE FUNCTION
7−4 RSVD R Reserved. Bits 7−4 return 0h when read.
3 CDCHANGE R
Card detect change. Bit 3 indicates whether a change on CD1 or CD2 occurred at the PC Card interface.
This bit is encoded as:
0 = No change detected on either CD1 or CD2
1 = Change detected on either CD1 or CD2
2 READYCHANGE R
Ready change. When a 16-bit memory is installed in the socket, bit 2 includes whether the source of an
interrupt was due to a change on READY at the PC Card interface, indicating that the PC Card is now
ready to accept new data. This bit is encoded as:
0 = No low-to-high transition detected on READY (default)
1 = Detected low-to-high transition on READY
When a 16-bit I/O card is installed, bit 2 is always 0b.
1 BATWARN R
Battery warning change. When a 16-bit memory card is installed in the socket, bit 1 indicates whether the
source of an interrupt was due to a battery-low warning condition. This bit is encoded as:
0 = No battery warning condition (default)
1 = Detected battery warning condition
When a 16-bit I/O card is installed, bit 1 is always 0b.
0 BATDEAD R
Battery dead or status change. When a 16-bit memory card is installed in the socket, bit 0 indicates
whether the source of an interrupt was due to a battery dead condition. This bit is encoded as:
0 = STSCHG deasserted (default)
1 = STSCHG
asserted
Ring indicate. When the controller is configured for ring indicate operation, bit 0 indicates the status of
RI
.
