
PRS28.4G
IBM Packet Routing Switch
prs28.03.fm
August 31, 2000
I/O Definitions and Timing
Page 107 of 131
7.1.2.2 RCV_GRANT Sampling Window
The sampling window of RCV_GRANT(n) is the time window during which the RCV_GRANT signals on the
device pins are sampled in order to decide on the reception of a packet for output n. This window is defined in
relationship with the beginning of the packet reception on the chip input pins.
7.1.2.3 Q_FULL, Q_EMPTY and Q_SYNC Bus
(Trb, Tre) and (Tfe, Tfb) defined windows in which the Q_FULL and Q_EMPTY bits will change value for a
new priority, in relation to Q_SYNC rising edge and falling edge respectively.
Figure 11: SND_GRANT(
n
)
Sampling Window in relationship with the packet flow on output
n
pins.
Table 26: SND_Grant Sampling Window Timing
Symbol
Parameter
Rating
Note
t
WB
Sampling Window Beginning
(including setup time)
21 ns + 18 byte cycles
1
t
WE
Sampling Window End
(including hold time)
17 ns + 18 byte cycles
1
1. Byte cycle = 9ns (111.1MHz operation) to 10ns (100MHz operation).
Figure 12: RCV_GRANT(
n
)
Sampling Window in relationship with the packet flow on any input.
Table 27: RCV_Grant Sampling Window Timing
Symbol
Parameter
Rating
Note
t
WB
Sampling Window Beginning - (including setup time)
-3 ns + 2 clock cycles
1
t
WE
Sampling Window End -
(including hold time)
14 ns + 5.25 clock cycles
1
1. Clock cycle = 9ns (111.1MHz operation) to 10ns (100MHz operation).
SND_GRANT (n) Sampling Window for packet M
Packet M-1
Packet M
Twe
Twb
Packet Transmission on DASL output pins of port n
RCV_GRANT (n) Sampling Window for packet M
Packet M
Packet M + 1
Twe
Twb
Packet Reception on DASL input pins