AM7968 AMD [Advanced Micro Devices], AM7968 Datasheet - Page 81

• Manufacturer Part Number: AM7968
• Description: TAXIchip Integrated Circuits(Transparent Asynchronous Xmitter-Receiver Interface)
• Manufacturer: AMD [Advanced Micro Devices]

STROBE
Figure 7-2
DATA
32
U1
Cascade with One TAXI Transmitter
7.2 Receivers In Cascade Mode: Connections (Am7969-125 Only)
Unlike transmitters, all cascaded receivers are directly connected to the media, via the
two serial input data lines. All Receivers see the same serial data at the same time. The
Primary Receiver always receives the first byte of serial data after a Sync. The signals
used by the upstream Receiver to tell the downstream Receiver that it has captured a
byte are IGM (I Got Mine) and CNB (Catch Next Byte). After receiving its byte, the
upstream receiver raises its IGM signal, telling the next Receiver in line that it is to catch
the next byte on the serial line. In this way each succeeding Receiver down the line
catches each succeeding byte.
The second receiver waits for the Primary Receiver to capture data before capturing its
data (the second byte). Similarly, if there were a third Receiver it would wait until the
second Receiver had captured the second byte before capturing the third byte.
The connections of the cascaded (downstream) TAXI Receivers are as follows (see
Figure 7-3):
The CNB input of the cascaded Receiver is tied to the IGM of it’s upstream neighbor.
The CNB input of the first upstream or primary Receiver is tied high.
The IGM output of the last downstream Receiver is left unconnected normally. (This pin
is used differently in Auto-repeat Configuration, discussed in section 7.3).
8
D
CK
D
CK
BUFFERS
74ALS374
DFF
OE-
BYTE1
Q
Q
LOAD1-
8
TAXIchip Integrated Circuits Technical Manual
8
BUFFERS
D
CK
D
CK
74ALS374
U7
BYTE2
DFF
OE-
Four-Byte Cascade Mode Logic
Q
Q
LOAD2-
8
8
74LS174
BUFFERS
D
CK
D
CK
74ALS374
DFF
OE-
BYTE3
Q
Q
LOAD3-
8
8
D
CK
D
BUFFERS
CK
74ALS374
DFF
OE-
BYTE4
Q
Q
8
LOAD4-
D
CK
DFF
Q
U2
8
LOADEN
STRBIN
U3
CLK2
U6
4
CLK
U5
U4
STRB
ACK
DATA
COMMAND
SEROUT
CLK
TAXI
CLK Buffer;
May Not Be
Required for
Low Fanout
System
AMD
ACK0
ACK1
CLK1
12330E-24
2
SEROUT
77