AM79C970A Advanced Micro Devices, AM79C970A Datasheet - Page 104

• Manufacturer Part Number: AM79C970A
• Description: PCnet-PCI II Single-Chip Full-Duplex Ethernet Controller for PCI Local Bus Product
• Manufacturer: Advanced Micro Devices

Double Word I/O Mode
The PCnet-PCI II controller can be configured to oper-
ate in DWord (32bit) I/O mode. The software can invoke
the DWIO mode by performing a DWord write access to
the I/O location at offset 10h (RDP). The data of the write
access must be such that it does not affect the intended
operation of the PCnet-PCI II controller. Setting the de-
vice into 32-bit I/O mode is usually the first operation af-
ter H_RESET or S_RESET. The RAP register will point
to CSR0 at that time. Writing a value of ZERO to CSR0
is a save operation. DWIO (BCR18, bit 7) will be set to
104
Offset
00h – 0Fh
10h
12h
14h
16h
18h – 1Fh
Table 19. I/O Map In Word I/O Mode (DWIO = 0)
AD[4:0]
0XX00
0XX01
0XX10
0XX11
0XX00
0XX10
0XX00
0XX10
10000
10010
10100
10110
10000
10010
10100
10110
10000
AMD
No. of Bytes
BE[3:0]
16
1110
1101
1011
0111
1100
0011
1100
0011
1100
0011
1100
0011
1100
0011
1100
0011
0000
2
2
2
2
8
Table 20. Legal I/O Accesses in Word I/O Mode (DWIO = 0)
Register
APROM
RDP
RAP (shared by RDP
and BDP)
Reset Register
BDP
Reserved
Type
WR
WR
WR
WR
WR
WR
WR
RD
RD
RD
RD
RD
RD
RD
RD
RD
RD
Comment
Byte Read of APROM Location 0h, 4h, 8h or Ch
Byte Read of APROM Location 1h, 5h, 9h or Dh
Byte Read of APROM Location 2h, 6h, Ah or Eh
Byte Read of APROM Location 3h, 7h, Bh or Fh
Word Read of APROM Locations 1h (MSB) and 0h (LSB), 5h and 4h, 8h
and 9h or Ch and Dh
Word Read of APROM Locations 3h (MSB) and 2h (LSB), 7h and 6h, Bh
and Ah or Fh and Eh
Word Read of RDP
Word Read of RAP
Word Read of Reset Register
Word Read of BDP
Word Write to APROM Locations 1h (MSB) and 0h (LSB), 5h and 4h, 8h
and 9h or Ch and Dh
Word Write to APROM Locations 3h (MSB) and 2h (LSB), 7h and 6h, Bh
and Ah or Fh and Eh
Word Write to RDP
Word Write to RAP
Word Write to Reset Register
Word Write to BDP
DWord Write to RDP, switches Device to DWord I/O Mode
P R E L I M I N A R Y
Am79C970A
All I/O resources must be accessed in word quantities
and on word addresses. The Address PROM locations
can also be read in byte quantities. The only allowed
DWord operation is a write access to the RDP,
which switches the device to DWord I/O mode. A read
access other than listed in the table below will yield
undefined data, a write operation may cause unex-
pected reprogramming of the PCnet-PCI II controller
control registers.
ONE as indicating that the PCnet-PCI II controller oper-
ates in 32-bit I/O mode.
Note that even though the I/O resource mapping
changes when the I/O mode setting changes, the RDP
location offset is the same for both modes. Once the
DWIO bit has been set to ONE, only H_RESET or
S_RESET can clear it to ZERO. The DWIO mode set-
ting is unaffected by setting the STOP bit.
The table below shows how the 32 bytes of address
space are used in DWord I/O mode.