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This page describes a generic serial control block designed to provide an interface to register-oriented logic. Up to 16 registers, each up to 16-bits wide are supported. The timing is very close to the timing described for input and output in the PicoBlaze? documentation (linked below).

For most applications, read operations can be accomplished by connecting a multiplexer to 'data_in controlled by addr_out. If external logic must be notified of a read operation (for a FIFO, i.e.) the 'rd_ena signal may be used.

For writing, capture the data on a rising clock edge when wr_ena is asserted.

It is assumed that the 'clk input is the same as used for external logic, and that an appropriate timing constraint on the clock period has been set.

The serial port is configured as follows (this may be changed in the source code):

  115200 baud
  8 data bits
  no parity
  1 stop bit
  no flow control

The program sends a one-line identification string followed by a '$ prompt and waits for input. It understands two commands:

  R n                n is a hex port number 0-f
  W n dddd           dddd is 16-bit data to write 0000-ffff

Each command should be terminated with an ascii CR character. All characters sent to the interface are echoed to the host. Each CR received from the host is echoed followed by an ascii LF.

In response to the 'r command 4 hex digits are sent followed by an ascii CR, LF sequence and a new '$ prompt.

In response to the 'w command a new $ prompt only is sent.

If any unrecognized character is seen in the input, the string 'ERR followed by CR, LF and a new '$ prompt is sent to the host.

Last modified 9 years ago Last modified on Nov 8, 2013, 10:17:53 AM