82C89_06 Datasheet, PDF (2/13 Pages) Intersil Corporation – CMOS Bus Arbiter

Functional Diagram
80C86/
S2
80C88
S1
STATUS
S0
CONTROL/
STRAPPING
OPTIONS
LOCK
CLK
CRQLCK
RESB
ANYRQST
IOB
82C89
ARBITRATION
STATUS
DECODER
MULTIBUS
INTERFACE
CONTROL
+5V
LOCAL
BUS
INTERFACE
GND
INIT
BCLK
BREQ
BPRN
BPRO
BUSY
CBRQ
MULTIBUS™
COMMAND
SIGNALS
AEN
SYSB/
RESB
SYSTEM
SIGNALS
MULTIBUS™ is an Intel Corp. trademark.
Pin Description
PIN
SYMBOL NUMBER TYPE
DESCRIPTION
V_CC
20
GND
10
V_CC: The +5V Power supply pin. A 0.1µF capacitor between pins 10 and 20 is recommended for decoupling.
GROUND.
S0, S1, S2 1, 18-19
I STATUS INPUT PINS: The status input pins from an 80C86, 80C88 or 8089 processor. The 82C89 decodes
these pins to initiate bus request and surrender actions. (See Table 1).
CLK
17
I CLOCK: From the 82C84A or 82C85 clock chip and serves to establish when bus arbiter actions are initiated.
LOCK
16
I LOCK: A processor generated signal which when activated (low) prevents the arbiter from surrendering the multi-
master system bus to any other bus arbiter, regardless of its priority.
CRQLCK
15
I COMMON REQUEST LOCK: An active low signal which prevents the arbiter from surrendering the multi-master
system bus to any other bus arbiter requesting the bus through the CBRQ input pin.
RESB
4
I RESIDENT BUS: A strapping option to configure the arbiter to operate in systems having both a multi-master
system bus and a Resident Bus. Strapped high, the multi-master system bus is requested or surrendered as a
function of the SYSB/RESB input pin. Strapped low, the SYSB/RESB input is ignored.
ANYRQST
14
I ANY REQUEST: A strapping option which permits the multi-master system bus to be surrendered to a lower
priority arbiter as if it were an arbiter of higher priority (i.e., when a lower priority arbiter requests the use of the
multi-master system bus, the bus is surrendered as soon as it is possible). When ANYRQST is strapped low, the
bus is surrendered according to Table A in Design Information. If ANYRQST is strapped high and CBRQ is
activated, the bus is surrendered at the end of the present bus cycle. Strapping CBRQ low and ANYRQST high
forces the 82C89 arbiter to surrender the multi-master system bus after each transfer cycle. Note that when
surrender occurs BREQ is driven false (high).
IOB
2
I IO BUS: A strapping option which configures the 82C89 Arbiter to operate in systems having both an IO Bus
(Peripheral Bus) and a multi-master system bus. The arbiter requests and surrenders the use of the multi-master
system bus as a function of the status line, S2. The multi-master system bus is permitted to be surrendered while
the processor is performing IO commands and is requested whenever the processor performs a memory
command. Interrupt cycles are assumed as coming from the peripheral bus and are treated as an IO command.
AEN
13
O ADDRESS ENABLE: The output of the 82C89 Arbiter to the processor’s address latches, to the 82C88 Bus
Controller and 82C84A or 82C85 Clock Generator. AEN serves to instruct the Bus Controller and address latches
when to three-state their output drivers.
INIT
6
I INITIALIZE: An active low multi-master system bus input signal used to reset all the bus arbiters on the multi-
master system bus. After initialization, no arbiters have the use of the multi-master system bus.
2
FN2980.2
February 27, 2006