S2020/S2021
HIPPI SOURCE/DESTINATION INTERFACE CIRCUITS
holding this input high will maintain an asserted
CONNECT signal on the HIPPI channel, while
DATA LATENCY
The data latency through the Destination device is
defined as the time between detection of the BURST
signal by the Destination device from the HIPPI, to
the presentation of the data to the FIFO on the TTL
data lines and the assertion of the DATA_VALID
line. The data latency ranges from 2 to 6 clock
cycles. There is no response by the Destination
device on the HIPPI channel to data reception.
dropping this input will deassert the CONNECT
signal (Disconnect Function). If a Connect Request
is rejected, holding this input high will maintain a
deasserted CONNECT signal on the HIPPI channel
(after the four cycle reject sequence) and disable
further Connect Requests, while dropping this input
will also maintain a deasserted CONNECT signal but
will enable further Connect Requests.
ACCEPT_REJECT (input) [ACCRJ]
CONNECT CONTROL
This input specifies the response to generate when
CONNECT_IN is asserted during a Connect Request.
A high on this input when CONNECT_IN is asserted
will generate an Accept response, i.e., the CONNECT
signal on the HIPPI channel will be asserted and will
remain asserted until a Disconnect Function is initiated
(CONNECT_IN is deasserted). A low on this input
when CONNECT_IN is asserted will generate a Reject
response, i.e., the CONNECT signal on the HIPPI
channel will be asserted for four cycles then fall and
remain deasserted until the response for the next
Connect Request is initiated. The ACCEPT_REJECT
signal needs to be valid only for the first cycle of the
asserted CONNECT_IN input.
Connection control is provided via the four signals in
the “Connect Control” area on the Host-side of the
Destination device. With this interface, the Host can
monitor when a Connect Request or Disconnect
Request comes in from the HIPPI Source, and then
initiate the appropriate action in response to the
request.
SOURCE_AVAILABLE (output) [SRCAV]
High indicates an active Source-to-Destination
INTERCONNECT signal while the Destination
device is in the on-line mode. Low indicates an
inactive Source-to-Destination INTERCONNECT
signal or the Destination device commanded to the
off-line or disabled mode.
Note: The host can have the Destination device
automatically respond to connection requests by
tying the CONNECT_REQUEST output to the
CONNECT_IN input. In this case, the ACCEPT/
REJECT signal would be used as an “available/busy”
signal. While ACCEPT/REJECT was held low all
connection requests would be rejected.
CONNECT_REQUEST (output) [CONRQ]
This signal indicates the state of the REQUEST signal
on the HIPPI channel. High indicates a Connect
Request function from the HIPPI channel, resulting
from an asserted REQUEST signal while the Desti-
nation device is in a functional operating mode with
Connect Requests enabled. Low indicates either a
false REQUEST signal on the HIPPI channel, a
disabled Connect Request at this device, or that the
Destination device is in a non-functional mode.
DATA/FIFO CONTROL
This interface provides control to the Destination
Host system over the flow of data transfers on the
HIPPI channel, and provides control of data transfer
from the Destination device into the Destination Host
system. It is intended for this interface to attach to an
external synchronous FIFO or DMA mechanism
which, in turn, attaches to the Destination Host
memory system. Recommended FIFO’s capable of
buffering 4 or more full Bursts are:
CONNECT_IN (input) [CONIN]
This signal controls the Connect Request and
Response functions of the Destination device on the
HIPPI channel. A low on this input will hold the
CONNECT signal on the HIPPI channel inactive, and
will enable the REQUEST signal from the HIPPI
channel to control the CONNECT_REQUEST output
of this Destination device.
IDT P/N 72225LB20 1K x 18 bits
IDT P/N 72235LB20 2K x 18 bits
IDT P/N 72245LB20 4K x 18 bits
During a Connect Request, asserting this input
initiates one of two responses to the Request;
Accept or Reject the Request. The desired response
is selected with the ACCEPT_REJECT input,
described next. If a Connect Request is accepted,
The signals of this interface can be divided into three
groups: Destination FLOW control, Destination FIFO
control, and HIPPI data control.
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AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
