National Instruments HPC467064, HPC167064 Universal Peripheral Interface, Shared Memory Support

Universal Peripheral Interface

The Universal Peripheral Interface (UPI) allows the HPC167064 to be used as an intelligent peripheral to anoth- er processor. The UPI could thus be used to tightly link two HPC167064’s and set up systems with very high data ex- change rates. Another area of application could be where a HPC167064 is programmed as an intelligent peripheral to a host system such as the Series 32000É microprocessor. Figure 27 illustrates how a HPC167064 could be used as an intelligent peripheral for a Series 32000-based application.

The interface consists of a Data Bus (port A), a Read Strobe (URD), a Write Strobe (UWR), a Read Ready Line (RDRDY), a Write Ready Line (WRRDY) and one Address Input (UA0). The data bus can be either eight or sixteen bits wide.

The URD and UWR inputs may be used to interrupt the HPC167064. The RDRDY and WRRDY outputs may be used to interrupt the host processor.

The UPI contains an Input Buffer (IBUF), an Output Buffer (OBUF) and a Control Register (UPIC). In the UPI mode, Port A on the HPC167064 is the data bus. UPI can only be used if the HPC167064 is in the Single-Chip mode.

Shared Memory Support

Shared memory access provides a rapid technique to ex- change data. It is effective when data is moved from a pe- ripheral to memory or when data is moved between blocks of memory. A related area where shared memory access proves effective is in multiprocessing applications where two CPUs share a common memory block. The HPC167064 supports shared memory access with two pins. The pins are the RDY/HLD input pin and the HLDA output pin. The user can software select either the Hold or Ready function by the state of a control bit. The HLDA output is multiplexed onto Port B.

The host uses DMA to interface with the HPC167064. The host initiates a data transfer by activating the HLD input of the HPC167064. In response, the HPC167064 places its system bus in a TRI-STATE Mode, freeing it for use by the host. The host waits for the acknowledge signal (HLDA) from the HPC167064 indicating that the sytem bus is free. On receiving the acknowledge, the host can rapidly transfer data into, or out of, the shared memory by using a conven- tional DMA controller. Upon completion of the message transfer, the host removes the HOLD request and the HPC167064 resumes normal operations.

To insure proper operation, the interface logic shown is rec- ommended as the means for enabling and disabling the us- er’s bus. Figure 28 illustrates an application of the shared memory interface between the HPC167064 and a Series 32000 system.

Memory

The HPC167064 has been designed to offer flexibility in memory usage. A total address space of 64 kbytes can be addressed with 8 kbytes of EPROM and 512 bytes of RAM available on the chip itself. The EPROM may contain pro- gram instructions, constants or data. The EPROM and RAM share the same address space allowing instructions to be executed out of RAM.

Program memory addressing is accomplished by the 16-bit program counter on a byte basis. Memory can be addressed directly by instructions or indirectly through the B, X and SP registers. Memory can be addressed as words or bytes. Words are always addressed on even-byte boundaries. The HPC167064 uses memory-mapped organization to support registers, I/O and on-chip peripheral functions.

The HPC167064 memory address space extends to 64 kbytes and registers and I/O are mapped as shown in Table III and Table IV.

TL/DD/11046 – 35

FIGURE 27. HPC167064 as a Peripheral (UPI Interface to Series 32000 Application)

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