Intel C2518 FH8065501516710 Data Sheet

Intel

Product codes

FH8065501516710

Volume 2—SMBus 2.0 Unit 0 - PCU—C2000 Product Family

System Host Controller

Intel

®

Atom™ Processor C2000 Product Family for Microserver

Datasheet, Vol. 2 of 3

September 2014

434

Order Number: 330061-002US

18.3.1.6

Block Read/Write Command

The SoC contains a 32-byte buffer for read and write data which are enabled by setting

SMB_Mem_AUXC.E32B, as opposed to a single byte of buffering. This 32-byte buffer is

filled with write data before transmission and filled with read data on reception. In the

SoC, the interrupt is generated only after a transmission or reception of 32 bytes, or

when the entire byte count has been transmitted/received.

When operating in I2C mode (SMB_Config_HCFG.I2C_EN bit is set), the SoC never

uses the 32-byte buffer for any block commands.

The byte count field is transmitted but ignored by the SoC as the software ends the

transfer after all bytes it cares about have been sent or received.

For a Block Write, the software must either force the SMB_Config_HCFG.I2C_EN bit or

both the SMB_Config_HCTL.PECEN and SMB_Mem_AUXC.AAC bits to 0b when running

The Block Write begins with a slave address and a write condition. After the command

code, the SoC issues a byte count describing how many more bytes follow in the

message. If a slave has 20 bytes to send, the first byte is the number 20 (14h),

followed by 20 bytes of data. The byte count is not 0. A Block Read or Write is allowed

to transfer a maximum of 32-data bytes.

When programmed for a Block Write command, the Transmit Slave Address

(SMB_Mem_TSA), Host Command (SMB_Mem_HCMD) and Data 0 (SMB_Mem_HD0)

registers are sent. Data is then sent from the Host Block Data (SMB_Mem_HBD)

register; the total data sent being the value stored in the Data 0 (SMB_Mem_HD0)

register. On Block Read commands, the first byte received is stored in the Data 0

(SMB_Mem_HD0) register, and the remaining bytes are stored in the Host Block Data

(SMB_Mem_HBD) register. See Section 5.5.7 of the System Management Bus (SMBus)

Specification, Version 2.0 for the format of the protocol.

Note:

For a Block Write, if the SMB_Config_HCFG.I2C_EN bit is set, the format of the

command changes slightly. The SoC still sends the number of bytes (on writes) or

receive the number of bytes (on reads) indicated in the Data 0 (SMB_Mem_HD0)

register. However, it does not send the contents of the Data 0 (SMB_Mem_HD0)

register as part of the message. Also, the block write protocol sequence changes

slightly: the byte count (bits [27:20] in the bit sequence) is not sent, and as a result,

the slave does not acknowledge (bit 28 in the sequence).