IDT PCI Express 89HPES32NT24xG2, User Manual, Page: 236 / 744

IDT SMBus Interfaces
PES32NT24xG2 User Manual 12 - 32 January 30, 2013
Notes
Examples of Setting Up the I2C CSR Byte Sequence for a CSR Register
Read
The pseudo examples below demonstrate the block transaction settings for a CSR register read. As an
example, in many of the IDT utilities the CSR byte sequence array is passed to a TotalPhase Aardvark I2C
control function.
Table 12.26 lists the constant variables used in this example of setting up the command byte array.
Step 1. Initialize a CSR register offset variable and a command code init variable
CSR_Offset = address shifted by 2 bits to the right
CCode_i = CCode_Init
5 0 0 Reserved. Must be zero
6 RERR Read-Only
and Clear
Read Error. This bit is set if the last CSR read SMBus transaction
was not claimed by a device. Success indicates that the transaction
was claimed and not that the operation completed without error.
7 WERR Read-Only
and Clear
Write Error. This bit is set if the last CSR write SMBus transaction
was not claimed by a device. Success indicates that the transaction
was claimed and not that the operation completed without error.
Constant Name Value Description
CCode_Block 0x40 [6:5] = 2 - Block option
CCode_Init 0x03 [0:0] = 1 - Current transaction is the last read or write sequence
[1:1] = 1 - Current transaction is the first of a read or write
sequence.
TranSize_BkWtHeader 3 Transaction block write header of size 3
TranSize_BkRdHeader 4 Transaction block read header of size 4
TranSize_Block 5 Transaction block size of 5
CMD_Init 0x00 [7:0] Initial CMD byte as zero
CMD_BELL 0x01 [0:0] Byte Enable Lower.
CMD_BELM 0x02 [1:1] Byte Enable Lower Middle.
CMD_BEUM 0x04 [2:2] Byte Enable Upper Middle.
CMD_BEUU 0x08 [3:3] Byte Enable Upper.
CMD_DWORD 0x0F [3:0] Enable BELL, BELM, BEUM, BEUU
CMD_OPRD 0x10 [4:4] Enable CSR Operation default as CSR Read
Len_Byte 1 Length of 1 (1 byte)
Len_Word 2 Length of 2 (2 bytes)
Len_Dword 4 Length of 4 (4 bytes)
Table 12.26 Constants Used in Examples
Bit
Field
Field
Name
Type Description
Table 12.25 CSR Register Read or Write CMD Field Description (Part 2 of 2)