IMX27L datasheet(17/122 Pages) FREESCALE

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Functional Description and Application Information

i.MX27/i.MX27L Data Sheet, Advance Information, Rev. 1

Freescale Semiconductor

Preliminary—Subject to Change Without Notice

2.3.17

IC Identification Module (IIM)

The IC identification module (IIM) provides an interface for reading and in some cases programming

and/or overriding identification and control information stored in on-chip fuse elements. The module

supports laser fuses (L-Fuses) or electrically-programmable poly fuses (e-Fuses) or both.

The IIM also provides a set of volatile software-accessible signals, which can be used for software control

of hardware elements not requiring non-volatility. The IIM provides the primary user-visible mechanism

for interfacing with on-chip fuse elements. Among the uses for the fuses are unique chip identifiers, mask

revision numbers, cryptographic keys, and various control signals requiring permanent non-volatility. The

IIM also provides up to 28 volatile control signals and an ability to generate a second 168-bit SCC key.

The IIM consists of a master controller, a software fuse value shadow cache, and a set of registers to hold

the values of signals visible outside the module. Up to eight arrays of fuses (L-Fuses and/or e-Fuses) are

associated with the IIM, but are instantiated outside of it.

The IIM is accessible via an 8-bit IP bus interface. An 8-bit interface is used because it matches the natural

width of the fuse arrays. All registers are 32-bit aligned to enable the module to be instantiated on IP buses

supporting only 32-bit peripherals. A subset of fuses, as well as the software-controlled volatile signals,

are capable of driving top-level nets within the SoC. These signals are hereinafter referred to as

Hardware-Visible Signals, or HW-Visible Signals. These signals are intended for feature enablement and

disablement and similar uses within the device.

Laser fuses can only be blown during chip manufacturing (at the wafer level). The e-Fuses may be blown

under software or JTAG control during the IC final test, in the customer’s factory, or in the field. They

include a mechanism to inhibit further blowing of fuses (write-protect) to support secure computing

environments. The fuse values may also be overridden by software without modifying the fuse element.

Similar to the write-protect functionality, the override functionality can also be permanently disabled. Fuse

banks may also be scan-inhibited on a per-bank basis to prevent reading and programming of fuses through

the JTAG interface.

2.3.18

JTAG Controller (JTAGC)

The JTAG controller (JTAGC) module supports debug access to the ARM926 Platform and tristate enable

of the I/O pads. The overall strategy is to achieve good test and debug features without increasing the pin

count and reducing the complexity of I/O muxing. The JTAG Controller is compatible with IEEE 1149.1

Standard Test Access Port and Boundary Scan Architecture.

2.3.19

Keypad Port (KPP)

The keypad port (KPP) is designed to interface with a keypad matrix with 2-contact or 3-point contact

keys. KPP is designed to simplify the software task of scanning a keypad matrix. With appropriate

software support, the KPP is capable of detecting, debouncing, and decoding one or multiple keys pressed

simultaneously in the keypad. The KPP supports up to 8

× 8 external key pad matrix. Its port pins can be

used as general purpose I/O. Using an open drain design, the KPP includes glitch suppression circuit

design, multiple keys, long key, and standby key detection.

IMX27L Datasheet(PDF) 17 Page - Freescale Semiconductor, Inc

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