CS8920A
ISA Bus Interface (continued)
Symbol
IOCS16
Pin Number
43
Type
Description
OD24
I/O Chip Select 16-bit:
Open-drain, active-low output generated by the
CS8920A when it recognizes an address on the ISA bus that
corresponds to its assigned I/O space. Tri-stated when not active.
OD24
I/O Channel Ready:
When driven low, this open-drain, active-high
output extends I/O Read and Memory Read cycles to the CS8920A. This
output is functional when the IOCHRDYE bit in the Bus Control register
(Register 17) is clear. This pin is always tri-stated when the IOCHRDYE
bit is set.
I
System Bus High Enable:
Active-low input indicates a data transfer on
the high byte of the System Data Bus (SD8-SD15). After a hardware or
software reset, provide a HIGH to LOW and then a LOW to HIGH
transition on SBHE signal before any IO or memory access isdone to the
CS8920A. *
O24ts
Interrupt Request:
Active-high output indicates the presence of an
interrupt event. The pin goes low after the host reads a non-zero value
from the Interrupt Status Queue (ISQ).
O24ts
DMA Request:
Active-high, tri-stateable output used by the CS8920A 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.
I
DMA Acknowledge:
Active-low input indicates acknowledgment by the
host of the corresponding DMA Request output.
IOCHRDY
92
SBHE
52
IRQ2/IRQ9
IRQ3-IRQ7
IRQ10-IRQ12
IRQ14-IRQ15
DRQ5
DRQ6
DRQ7
DACK5
DACK6
DACK7
106
75-79
34-32
30-31
16
14
9
17
15
10
EEPROM and Boot PROM Interface
Symbol
EESK
EECS
EEDI
Pin Number
142
141
7
Type
Description
O4
EEPROM Serial Clock:
Serial clock used to clock data into or out of the
EEPROM.
O4
EEPROM Chip Select:
Active-high output used to select the EEPROM.
Iw
EEPROM Data In:
Serial input used to receive data from the EEPROM.
Connects to the DO pin on the EEPROM. EEDI is also used to sense the
presence of the EEPROM.
O4
EEPROM Data Out:
Serial output used to send data to the EEPROM.
Connects to the DI pin on the EEPROM. When TEST is low, this pin
becomes the output for the Boundary Scan Test.
O4
Chip Select for External Boot PROM:
Active-low output used to select
an external Boot PROM when the CS8920A decodes a valid Boot PROM
memory address.
=
=
=
Input
Output
Power
G
ts
w
=
=
=
Ground
Tri-State
Internal Weak Pullup
EEDO
6
CSOUT
8
Pin Types:
dI = Differential Input Pair
I
dO = Differential Output Pair
O
B = Bi-Directional with Tri-State Output P
OD = Open Drain Output
Digital outputs are followed by drive in mA (Example:
OD24 = Open Drain Output with 24 mA drive).
* For operation of the CS8920A in 16 bit mode, a transition on the SBHE line is required after a hardware or
software reset.
DS238PP2
11
CIRRUS [ CIRRUS LOGIC ]
