AMD
Fig u re 7 -2
Ca s c a d e w it h On e TAXI Tra n s m it t e r
U7
74LS174
ACK0
ACK1
LOAD1-
LOAD2-
LOAD3-
LOAD4-
U1
STROBE
D
Q
D
Q
DFF
D
Q
DFF
D
Q
DFF
D
Q
DFF
DFF
CK
CK
CK
CK
CK
CLK2
U6
CLK1
U5
CLK Buffer;
May Not Be
Required for
Low Fanout
System
U3
U2
U4
LOADEN
STRBIN
32
DATA
CLK
8
8
8
8
CLK
OE-
OE-
OE-
OE-
D
Q
D
Q
D
Q
D
Q
BUFFERS
BUFFERS
BUFFERS
BUFFERS
STRB
CK
CK
CK
CK
SEROUT
ACK
2
74ALS374
74ALS374
74ALS374
74ALS374
SEROUT
8
8
8
8
TAXI
DATA
BYTE1
BYTE2
BYTE3
BYTE4
8
4
COMMAND
12330E-24
Four-Byte Cascade Mode Logic
7 .2 Re c e ive rs In Ca s c a d e Mo d e : Co n n e c t io n s (Am 7 9 6 9 -1 2 5 On ly)
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).
77
TAXIchip Integrated Circuits Technical Manual
AMD [ AMD ]
