Device Registers; General; Pci Memory Map; Device Register Description - Symmetricom bc635PCI-V2 User Manual

1. PCI/PCIe TFP Hardware

1.4. Device Registers

1.4.1. General

The Time & Frequency Processor (TFP) is controlled by a combination of hardware device registers
and a dual-port RAM interface. This chapter describes the TFP device registers. "1.5. Dual-Port RAM
Interface" on page 35 describes the dual-port RAM interface.

1.4.2. PCI Memory Map

The TFP is divided into two 2K memory spaces, Dual-Port RAM and Register. The following table
lists the card's physical memory map.
TFP Physical Memory Map
Start Type
PCI Auto R/W
PCI Auto R/W

1.4.3. Device Register Description

The TFP device registers are 32-bits wide (PCI word size). For many of the registers, only a few of
the bits have any significance while the rest of the bits are ignored during writes and are meaningless
during reads. Registers may be:
Read only (R)
l
Write only (W)
l
Read/write (R/W)
l
Access (A)
l
Access type registers perform a function simply by being read or written without regard to the data
contents. It is best to use a write operation with the access type registers because most optimizing
compilers will remove statements that read a register but do nothing with the data returned. In some
cases, a read/write register is structured to support dissimilar data in the read and write directions.
The following table summarizes the type of register located at each offset and provides a brief descrip-
tion of the register function.
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Size
0x800
0x50 (0x800 reserved)
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Register Field
Dual Port RAM
Device Registers