AM79C976 Advanced Micro Devices, AM79C976 Datasheet - Page 47

• Manufacturer Part Number: AM79C976
• Description: PCnet-PRO 10/100 Mbps PCI Ethernet Controller
• Manufacturer: Advanced Micro Devices

Figure 17 shows a target abort sequence. The target
asserts DEVSEL for one clock. It then deasserts
DEVSEL and asserts STOP on clock 4. A target can
use the target abort sequence to indicate that it can-
not service the data transfer and that it does not want
the transaction to be retr ied. Additionally, the
Am79C976 controller cannot make any assumption
about the success of the previous data transfers in the
current transaction. The Am79C976 controller termi-
nates the current transfer with the deassertion of
8/01/00
DEVSEL
FRAME
STOP
TRDY
C/BE
IRDY
REQ
GNT
CLK
PAR
AD
DEVSEL is sampled
1
2
ADDR i
0111
3
P R E L I M I N A R Y
PAR
4
DATA
0000
Am79C976
5
PAR
FRAME on clock 5 and of IRDY one clock cycle later.
It finally releases the bus on clock 6.
Since data integrity is not guaranteed, the Am79C976
controller cannot recover from a target abort event. The
Am79C976 controller will reset all CSR locations to their
STOP_RESET values. The BCR and PCI configuration
registers will not be cleared. Any on-going network
transmission is terminated with the current FCS invert-
ed and appended at the next byte boundary. This guar-
antees that the receiving station will drop the truncated
frame.
6
7
8
9
10
ADDR i
0111
11
22929B18
47