4 TCG PC Client Platform TPM Profile (PTP) Specification Summary

The Microchip TPM SPI communications protocol is implemented in accordance with the TCG PC Client Platform TPM Profile (PTP) Specification 1.3. A complete description of the protocol is contained in the specification available at www.trustedcomputinggroup.org. It is recommended that application development and platform system design be based on the TCG PTP specification.

TPM_DID_VID_x Register

The TPM_DID_VID_x register contains Device ID (DID) and Vendor ID (VID) information. The VID register contents are assigned by the TCG Administration and contain the hex string 0x01 0x01 0x01 0x04.

DID Register

The ATTPM20P DID register contains the device ID information and this is set to 0x03 0x02 0x00 0x05.

TPM_RID_x register

The ATTPM20P Revision ID (RID) register is a single byte register containing revision information. Current value is set to 0x01.

Firmware Revision Information

The current firmware revision can be found by executing the TCG TPM2_GetCapability command.

Important: Per the TCG specification, the TPM2_Startup command must be issued to the TPM device before any other command can be executed successfully. This includes the TPM2_GetCapability command.
Table 4-1. TCG formatted input command structure:Raw input: 80 01 00 00 00 16 00 00 01 7A 00 00 00 06 00 00 01 0B 00 00 00 01
NameValue
tag0x80 0x01
commandSize0x00 0x00 0x00 0x16
commandCode0x00 0x00 0x01 0x7A
capability0x00 0x00 0x00 0x06 (TPM_CAP_TPM_PROPERTIES)
property0x00 0x00 0x01 0x0B (TPM_PT_FIRMWARE_VERSION_1)
propertyCount0x00 0x00 0x00 0x01
Table 4-2. TCG formatted Output Command Structure:Expected Output: 80 01 00 00 00 1B 00 00 00 00 01 00 00 00 06 00 00 00 01 00 00 01 0B 02 00 50 XX
NameValue
tag0x80 0x01
responseSize0x00 0x00 0x00 0x1B
responseCode0x00 0x00 0x00 0x00
moreData0x01
capability0x00 0x00 0x00 0x06 (TPM_CAP_TPM_PROPERTIES)
propertyCount0x00 0x00 0x00 0x01
property0x00 0x00 0x01 0x0B (TPM_PT_FIRMWARE_VERSION_1)
Firmware Version0x02 0x00 0x50 0xXX