CS8900-CQ3 Cirrus Logic, CS8900-CQ3 Datasheet - Page 26

• Manufacturer Part Number: CS8900-CQ3
• Description: Crystal LAN ISA Ethernet Controller
• Manufacturer: Cirrus Logic

BootPROM Address Mask register (PacketPage
base + 0034h). The Boot PROM Base Address pro-
vides the starting location in host memory where
the Boot PROM is mapped. The Boot PROM Ad-
dress Mask indicates the size of the attached Boot
PROM and is limited to 4-Kbyte increments. The
lower 12 bits of the Address Mask are ignored and
should be 000h.
In the EEPROM example shown in Table 6, the
Boot PROM starting address is D0000h and the
Address Mask is FC000h. This configuration de-
scribes a 16-Kbyte (128 Kbit) PROM mapped into
host memory from D0000h to D3FFFh.
3.7 Low-Power Modes
For power-sensitive applications, the CS8900A
supports three low-power modes: Hardware Stand-
by, Hardware Suspend, and Software Suspend. All
three low-power modes are controlled through the
SelfCTL
Section 4.4.4 on page 49.
An internal reset occurs when the CS8900A comes
out of any suspend or standby mode. After a reset
(internal or external), the CS8900A goes through a
self configuration. This includes calibrating on-
chip analog circuitry, and reading EEPROM for va-
lidity and configuration. When the calibration is
done, bit InitD in Register 16 (Self Status register)
is set indicating that initialization is complete, and
the SIBUSY bit in the same register is cleared (in-
26
CS8900A
CSOUT
(Pin 17)
SA(0:14)
Figure 6. Boot PROM Connection Diagram
20
22
register
CE
OE
27C256
(Register
19
OE
DIR
B1
B8
74LS245
.
.
.
CIRRUS LOGIC PRODUCT DATA SHEET
15).
A1
A8
.
.
.
SD(0:7)
See
also
BUS
ISA
dicating that the EEPROM is no longer being read
or programmed. Time required for the reset calibra-
tion is typically 10 ms. Software drivers should not
access registers internal to CS8900A during this
time.
3.7.1 Hardware Standby
Hardware (HW) Standby is designed for use in sys-
tems, such as portable PC’s, that may be temporari-
ly disconnected from the 10BASE-T cable. It
allows the system to conserve power while the
LAN is not in use, and then automatically restore
Ethernet operation once the cable is reconnected.
In HW Standby mode, all analog and digital cir-
cuitry in the CS8900A is turned off, except for the
10BASE-T receiver which remains active to listen
for link activity. If link activity is detected, the
LANLED pin is driven low, providing an indica-
tion to the host that the network connection is ac-
tive. The host can then activate the CS8900A by
deasserting the SLEEP pin. During this mode, all
ISA bus accesses are ignored.
To enter HW Standby mode, the SLEEP pin must
be low and the HWSleepE bit (Register 15, Self-
CTL, Bit 9) and the HWStandbyE bit (Register 15,
SelfCTL, Bit A) must be set. When the CS8900A
enters HW Standby, all registers and circuits are re-
set except for the SelfCTL register. Upon exit from
HW Standby, the CS8900A performs a complete
reset, and then goes through normal initialization.
3.7.2 Hardware Suspend
During Hardware Suspend mode, the CS8900A
uses the least amount of current of the three low-
power modes. All internal circuits are turned off
and the CS8900A’s core is electronically isolated
from the rest of the system. Accesses from the ISA
bus and Ethernet activity are both ignored.
HW Suspend mode is entered by driving the
SLEEP pin low and setting the HWSleepE bit
(Register 15, SelfCTL, bit 9) while the HWStand-
byE bit (Register 15, SelfCTL, bit A) is clear. To
Crystal LAN™ ISA Ethernet Controller
CS8900A
DS271PP3