Hardware Reference Manual
421 Intelligent Serial, 8-Port
2.1.1 PCI Interface
The PMC421 PCI interface is compliant with revision 2.1 of the specification. It supports up to 33MHz operation
with 32-bit data path. Functions within the interface that augment the operation of the PMC421 include:
•
DMA engines to move larger data packets efficiently over the bus
•
Message passing hardware supporting simple and efficient application API
2.1.2 IOCP
The IOCP (Intelligent Co-processor) refers to the local CPU, which executes the PMC421 firmware. It is a full
function, 32-bit RISC processor. The firmware is based upon the open source Real Time Operating System
(RTOS) RTEMS which was developed by the US Army. It provides all functionality expected from an embedded
kernel, and strongly enhances the modularity of the RAMiX firmware design. The basic firmware handles off-
standard functions (e.g., UART configuration, block and character oriented data transfer, etc.).
Initial configuration is extremely simple, as is operational use. This is a result of having all detailed control of the
UART performed by the firmware library. In most software device drivers, a substantial component (and usually
much of the complexity) is in device-specific setup. All of this is performed by easily invoked library functions.
The firmware uses the DMA engines whenever possible to maximize PCI efficiency. Again, the benefit of using
the dedicated IOCP is apparent. DMA engine setup is not required by the host, as the IOCP will master all data
movement.
2.1.3 UART
The UART components chosen for the PMC421 are recent implementations that provide enhanced features and
small package size. Features include deep FIFO hardware buffers for each port (128 Bytes per port) as well as a
number of on-chip capabilities to maintain full wire speed while minimizing timing constraints on the IOCP. Each
port is configured independently for baud rate and flow control options. Full modem or three wire operation can
be selected on a “per port” basis.
2.1.4 Signaling Drivers
A design goal of the PMC421 was to maximize the amount of configuration that can be done under software
control, including setting of the electrical signaling characteristics. Each port can be set to RS232, RS422 or
RS485 signaling standard under software control of the IOCP.
DDC No. Rx-URMH 002 Rev -
Issued 12 November 2002
9 of 19
