diff options
Diffstat (limited to 'Documentation/i2c')
| -rw-r--r-- | Documentation/i2c/smbus-protocol.rst | 14 | ||||
| -rw-r--r-- | Documentation/i2c/summary.rst | 8 |
2 files changed, 13 insertions, 9 deletions
diff --git a/Documentation/i2c/smbus-protocol.rst b/Documentation/i2c/smbus-protocol.rst index 9e07e6bbe6a3..00d8e17d0aca 100644 --- a/Documentation/i2c/smbus-protocol.rst +++ b/Documentation/i2c/smbus-protocol.rst @@ -36,6 +36,8 @@ Key to symbols =============== ============================================================= S Start condition +Sr Repeated start condition, used to switch from write to + read mode. P Stop condition Rd/Wr (1 bit) Read/Write bit. Rd equals 1, Wr equals 0. A, NA (1 bit) Acknowledge (ACK) and Not Acknowledge (NACK) bit @@ -100,7 +102,7 @@ Implemented by i2c_smbus_read_byte_data() This reads a single byte from a device, from a designated register. The register is specified through the Comm byte:: - S Addr Wr [A] Comm [A] S Addr Rd [A] [Data] NA P + S Addr Wr [A] Comm [A] Sr Addr Rd [A] [Data] NA P Functionality flag: I2C_FUNC_SMBUS_READ_BYTE_DATA @@ -114,7 +116,7 @@ This operation is very like Read Byte; again, data is read from a device, from a designated register that is specified through the Comm byte. But this time, the data is a complete word (16 bits):: - S Addr Wr [A] Comm [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P + S Addr Wr [A] Comm [A] Sr Addr Rd [A] [DataLow] A [DataHigh] NA P Functionality flag: I2C_FUNC_SMBUS_READ_WORD_DATA @@ -164,7 +166,7 @@ This command selects a device register (through the Comm byte), sends 16 bits of data to it, and reads 16 bits of data in return:: S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] - S Addr Rd [A] [DataLow] A [DataHigh] NA P + Sr Addr Rd [A] [DataLow] A [DataHigh] NA P Functionality flag: I2C_FUNC_SMBUS_PROC_CALL @@ -181,7 +183,7 @@ of data is specified by the device in the Count byte. :: S Addr Wr [A] Comm [A] - S Addr Rd [A] [Count] A [Data] A [Data] A ... A [Data] NA P + Sr Addr Rd [A] [Count] A [Data] A [Data] A ... A [Data] NA P Functionality flag: I2C_FUNC_SMBUS_READ_BLOCK_DATA @@ -212,7 +214,7 @@ This command selects a device register (through the Comm byte), sends 1 to 31 bytes of data to it, and reads 1 to 31 bytes of data in return:: S Addr Wr [A] Comm [A] Count [A] Data [A] ... - S Addr Rd [A] [Count] A [Data] ... A P + Sr Addr Rd [A] [Count] A [Data] ... A P Functionality flag: I2C_FUNC_SMBUS_BLOCK_PROC_CALL @@ -300,7 +302,7 @@ This command reads a block of bytes from a device, from a designated register that is specified through the Comm byte:: S Addr Wr [A] Comm [A] - S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P + Sr Addr Rd [A] [Data] A [Data] A ... A [Data] NA P Functionality flag: I2C_FUNC_SMBUS_READ_I2C_BLOCK diff --git a/Documentation/i2c/summary.rst b/Documentation/i2c/summary.rst index 136c4e333be7..786c618ba3be 100644 --- a/Documentation/i2c/summary.rst +++ b/Documentation/i2c/summary.rst @@ -11,9 +11,11 @@ systems. Some systems use variants that don't meet branding requirements, and so are not advertised as being I2C but come under different names, e.g. TWI (Two Wire Interface), IIC. -The official I2C specification is the `"I2C-bus specification and user -manual" (UM10204) <https://www.nxp.com/docs/en/user-guide/UM10204.pdf>`_ -published by NXP Semiconductors. +The latest official I2C specification is the `"I2C-bus specification and user +manual" (UM10204) <https://www.nxp.com/webapp/Download?colCode=UM10204>`_ +published by NXP Semiconductors. However, you need to log-in to the site to +access the PDF. An older version of the specification (revision 6) is archived +`here <https://web.archive.org/web/20210813122132/https://www.nxp.com/docs/en/user-guide/UM10204.pdf>`_. SMBus (System Management Bus) is based on the I2C protocol, and is mostly a subset of I2C protocols and signaling. Many I2C devices will work on an |