CS8900A
Crystal LAN™ ISA Ethernet Controller
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, provide a HIGH to LOW and then LOW to HIGH
transition on SBHE signal before any IO or memory access is done to the CS8900A.
INTRQ[0:2] - 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 79.)
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.
EECS - EEPROM Chip Select, PIN 3.
Active-high output used to select the EEPROM.
CIRRUS LOGIC PRODUCT DATA SHEET
14
DS271PP3
CIRRUS [ CIRRUS LOGIC ]
