am79c970 Advanced Micro Devices, am79c970 Datasheet - Page 26

• Manufacturer Part Number: am79c970
• Description: Pcnettm-pci Single-chip Ethernet Controller For Pci Local Bus
• Manufacturer: Advanced Micro Devices

Basic Burst Write Cycles
The PCnet-PCI controller provides a burst mode to write
data to the receive buffer. The burst mode must be en-
abled by setting BWRITE in BCR18. All PCnet-PCI con-
troller burst write transfers are of the PCI command type
Memory Write (type 7). AD[1:0] will both be ZERO dur-
ing the address phase indicating a linear burst order. All
four byte enable signals will be ZERO during the data
phase as the PCnet-PCI controller always writes a full
32-bit word when in burst mode.
DEVSEL
FRAME
TRDY
IRDY
C/BE
REQ
GNT
PAR
CLK
AD
1
DEVSEL is sampled by the PCnet-PCI controller.
2
3
Figure 6. Burst Write Cycles
ADDR
0111
P R E L I M I N A R Y
4
Am79C970
DATA
PAR
5
0000
Figure 6 shows a typical burst write access. The PCnet-
PCI controller arbitrates for the bus, is granted access,
and writes four 32-bit words (DWORDs) from system
memory and then releases the bus. In this example, the
memory system extends the data phase of the first ac-
cess by one wait state. The following three data phases
take one clock cycle each, which is determined by the
timing of TRDY.
PAR
6
DATA
7
DATA
PAR
8
DATA
PAR
9
PAR
10
18220C-8
AMD
1-893