Broadcom PLX PCI 9052RDK-LITE, Справочник по аппаратуре

Страница: 17 / 39

3.4 Local Bus Operating Modes
The PCI 9052 local bus can be programmed to operate in 8- or 16-bit ISA bus mode, 8-,16-, or 32-bit
non-multiplexed address/data bus mode (C-Mode) or 8-, 16-, or 32-bit multiplexed address/data bus (J-
Mode). Programming of the PCI 9052 local bus operation is controlled by the value on the device’s
MODE pins and INTCSR[12] during power-up.
Byte and word local bus accesses are supported in ISA mode, allowing the bus to be populated with 8-
and 16-bit wide devices. Byte, word and long word access are supported in C-Mode and J-Mode, allowing
the bus to be populated with 8-, 16-, and 32-bit wide devices. The local bus ROM and SRAM can be
accessed in all operating modes.
The board ships in ISA mode, allowing customers to connect their own ISA cards to the PCI 9052RDK-
LITE. This facilitates the rapid conversion of ISA bus designs to PCI bus designs. Refer to Table 3-4
Configuration Jumper Settings to reconfigure the local bus operating mode. When operating in ISA mode,
Local Address Spaces 0 and 1 are used for ISA memory and ISA I/O accesses respectively and the local
bus control signals reflect this. However, any accesses to Local Address Spaces 2 and 3 will result in a
normal C mode transaction on the local bus. If Local Address Spaces 2 and 3 are disabled then only the
ISA interface is available on the local bus.
3.4.1 ISA Interface
The PCI 9052RDK-LITE board includes a single ISA socket to allow ISA cards to be accessed via the PCI
bus. The PCI 9052 is connected to this socket without any glue logic. If the designer has an existing ISA
card design that needs to be migrated to PCI, the designer can plug the existing ISA card into the ISA
socket on the RDK and immediately begin developing software on a familiar hardware platform.
The reader should note that there are a few minor exceptions to ISA compatibility. The PCI 9052RDK-
LITE board does not provide –5V to the ISA interface connector. Also, the PCI 9052 does not support ISA
mastering nor ISA DMA operations.
Later in the development cycle, when designing the new PCI card hardware, the designer can choose
whether to use the ‘ISA’ mode of the local bus or the multiplexed or non-multiplexed modes. The standard
multiplexed and non-multiplexed PCI 9052 local bus modes are very simple to interface to and may result
in a much simpler solution than using the ISA mode of the local bus and ISA interface logic from the
original ISA card.
3.5 Static RAM (SRAM)
Four 5V, 9ns, 32Kx8 Static RAMs (U7, U10, U15 and U16) are used on the RDK board. The SRAM is
accessible through the local bus. By default, CS2# is used to access the SRAM but the RDK can be
configured by JP2 to use any CS# for the SRAM socket. Refer to Table 3-4 Configuration Jumper
Settings to use another chip select signal to access the SRAM.
The SRAM can also be accessed by a local bus master by driving the XCSRAM# signal on the CPLD
(prototyping pad PC6) in conjunction with the local bus address, data, control and bus arbitration signals.
The PLXMon software can be used to read and write the SRAM. Refer to the PLXMon User’s Manual on
the SDK CD-ROM for more details. PLXMon allows the designer to view and modify data contents without
writing any code.
3.6 ROM Socket
A 32-pin PLCC socket is provided on the RDK. This can be used to install a 3.3V or 5V, 512Kx8 ROM or
Flash ROM memory device for storing code, either for an expansion ROM or to boot a microprocessor.
The socket is pre-connected to address, data and control lines, GND & VCC. By default, CS3# is used to
access the ROM socket but the RDK can be configured by JP2 to use any CS# for the ROM socket.
Refer to Table 3-4 Configuration Jumper Settings to use another chip select signal to access the SRAM.
PCI 9052RDK-LITE Hardware Reference Manual v1.3
© 2004 PLX Technology, Inc. All rights reserved . 9