Cirrus Logic CS8900A - Manual (Page 14)

14 DS271F5
CS8900A
Crystal LAN™ Ethernet Controller
CIRRUS LOGIC PRODUCT DATASHEET
IOW - I/O Write, Input PIN 62.
When IOW is low and a valid address is detected, the CS8900A writes the data on the
System Data Bus into the selected 16-bit I/O register. IOW is ignored if REFRESH is
low.
IOCS16 - I/O Chip Select 16-bit, Open Drain Output PIN 33.
Open-drain, active-low output generated by the CS8900A when it recognizes an
address on the ISA bus that corresponds to its assigned I/O space. 3-Stated when not
active.
IOCHRDY - I/O Channel Ready, Open Drain Output PIN 64.
When driven low, this open-drain, active-high output extends I/O Read and Memory
Read cycles to the CS8900A. This output is functional when the IOCHRDYE bit in the
Bus Control register (Register 17) is clear. This pin is always 3-Stated when the
IOCHRDYE bit is set.
SBHE - System Bus High Enable, Input PIN 36.
Active-low input indicates a data transfer on the high byte of the System Data Bus
(SD8-SD15). After a hardware or a software reset, the CS8900A will be in 8-bit mode.
Provide a HIGH to LOW and then LOW to HIGH transition on the SBHE signal before
any 16-bit IO or memory access is done to the CS8900A.
INTRQ[0:3] - Interrupt Request, 3-State PINS 30-32, 35.
Active-high output indicates the presence of an interrupt event. Interrupt Request goes
low once the Interrupt Status Queue (ISQ) is read as all 0's. Only one Interrupt
Request output is used (one is selected during configuration). All non-selected
Interrupt Request outputs are placed in a high-impedance state. (Section 3.2 on
page 18 and Section 5.1 on page 78.)
DMARQ[0:2] - DMA Request, 3-State PINS 11, 13, and 15.
Active-high, 3-Stateable output used by the CS8900A to request a DMA transfer. Only
one DMA Request output is used (one is selected during configuration). All non-
selected DMA Request outputs are placed in a high-impedance state.
DMACK[0:2] - DMA Acknowledge, Input PINS 12, 14, and 16.
Active-low input indicates acknowledgment by the host of the corresponding DMA
Request output.
CHIPSEL - Chip Select, Input PIN 7.
Active-low input generated by external Latchable Address bus decode logic when a
valid memory address is present on the ISA bus. If Memory Mode operation is not
needed, CHIPSEL should be tied low. The CHIPSEL is ignored for IO and DMA mode
of the CS8900A.
EEPROM and Boot PROM Interface
EESK - EEPROM Serial Clock, PIN 4.
Serial clock used to clock data into or out of the EEPROM.