Spectracom TPRO-cPCI, User Manual, Page: 23 / 46

Spectracom Corporation TPRO-cPCI/TSAT-cPCI
Synchronizable Timecode Generator User Manual 4-1
4 Register Level Description
NOTE: In this manual, the prefix "0x" indicates that the number is in hexadecimal (Base 16)
format. The descriptor “\0” denotes a single ASCII “null” character, which as a value
of zero (0x00). It indicates the end of an ASCII string.
4.1 Base Address
All accesses to the board consist of reading or writing 32-bit word values. The base address is
assigned at power-on by the BIOS software. The absolute memory address is computed as the
Base Address plus a constant Offset. Addresses count bytes (8 bits), but data is transferred as
words (32 bits). Thus, the offset for each register is a number evenly divisible by four.
NOTE: Some of the registers use less than 32-bits. For the sake of clarity, only those bits
actually used are described in this manual. All unused bits must be ignored in order to
maintain compatibility with future revisions.
4.2 ASCII Strings
Some of the commands and responses consist of ASCII strings. Four ASCII bytes are grouped
together in a single 32-bit word. The first character in the string is in the lowermost part of the
word (bits 07:00), the next character byte is in bits 15:08, the next is in bits 23:16, and the fourth
character in the string is in bits 31:24. For responses, which use more than four characters, the
fifth character is in bits 07:00 of the word located at the next (higher) address, etc.
The “null” character denotes the end of an ASCII string. This is a single 8-bit number, value
0x00, and is written as "\0" in this manual. For example, the string "TEST12.3456\0" stored in
the Response Register (tbreg_response[0] through tbreg_response[3]) would appear in memory
as:
Offset Contents Description
0x30 0x54534554 'T' 'S' 'E' 'T'
0x34 0x332e3231 '3' '.' '2' '1'
0x38 0x00363534 '\0' '6' '5' '4'
0x3c 0x????1234
Η
Echo of command 0x1234
Η
Denotes an undefined value
Not all commands and responses are ASCII strings. Some use straight binary format, and
others use Binary Coded Decimal (BCD) format.