GPMC
•
ERRORNOTSUPPADD occurs when an incoming system request address decoding does not match
any valid chip-select region, or if two chip-select regions are defined as overlapped, or if a register file
access is tried outside the valid address range of 1KB.
•
ERRORNOTSUPPMCMD occurs when an unsupported command request is decoded at the L3 Slow
interconnect interface
•
ERRORTIMEOUT: A time-out mechanism prevents the system from hanging. The start value of the
9-bit time-out counter is defined in the GPMC_TIMEOUT_CONTROL register and enabled with the
GPMC_TIMEOUT_CONTROL[0] TIMEOUTENABLE bit. When enabled, the counter starts at start-cycle
time until it reaches 0 and data is not responded to from memory, and then a time-out error occurs. When
data are sent from memory, this counter is reset to its start value. With multiple accesses (asynchronous
page mode or synchronous burst mode), the counter is reset to its start value for each data access within
the burst.
The GPMC does not generate interrupts on these errors. True abort to the MPU or interrupt generation is
handled at the interconnect level.
7.1.3.3.9 Timing Setting
The GPMC offers the maximum flexibility to support various access protocols. Most of the timing
parameters of the protocol access used by the GPMC to communicate with attached memories or devices
are programmable on a chip-select basis. Assertion and deassertion times of control signals are defined to
match the attached memory or device timing specifications and to get maximum performance during
accesses. For more information on GPMC_CLK and GPMC_FCLK see
In the following sections, the start access time refer to the time at which the access begins.
7.1.3.3.9.1 Read Cycle Time and Write Cycle Time (RDCYCLETIME / WRCYCLETIME)
The GPMC_CONFIG5_i[4-0] RDCYCLETIME and GPMC_CONFIG5_i[12-8] WRCYCLETIME fields define
the address bus and byte enables valid times for read and write accesses. To ensure a correct duty cycle
of GPMC_CLK between accesses, RDCYCLETIME and WRCYCLETIME are expressed in GPMC_FCLK
cycles and must be multiples of the GPMC_CLK cycle. RDCYCLETIME and WRCYCLETIME bit fields can
be set with a granularity of 1 or 2 throught GPMC_CONFIG1_i[4] TIMEPARAGRANULARITY.
When either RDCYCLETIME or WRCYCLETIME completes, if they are not already deasserted, all control
signals (CSn, ADV_ALEn, OE_REn, WEn, and BE0_CLEn) are deasserted to their reset values,
regardless of their deassertion time parameters.
An exception to this forced deassertion occurs when a pipelined request to the same chip-select or to a
different chip-select is pending. In such a case, it is not necessary to deassert a control signal with
deassertion time parameters equal to the cycle-time parameter. This exception to forced deassertion
prevents any unnecessary glitches. This requirement also applies to BE signals, thus avoiding an
unnecessary BE glitch transition when pipelining requests.
If no inactive cycles are required between successive accesses to the same or to a different chip-select
(GPMC_CONFIG6_i[7] CYCLE2CYCLESAMECSEN = 0 or GPMC_CONFIG6_i[6]
CYCLE2CYCLEDIFFCSEN = 0, where i = 0 to 3), and if assertion-time parameters associated with the
pipelined access are equal to 0, asserted control signals (CSn, ADV_ALEn, BE0_CLEn, WEn, and
OE_REn) are kept asserted. This applies to any read/write to read/write access combination.
If inactive cycles are inserted between successive accesses, that is, CYCLE2CYCLESAMECSEN = 1 or
CYCLE2CYCLEDIFFCSEN = 1, the control signals are forced to their respective default reset values for
the number of GPMC_FCLK cycles defined in CYCLE2CYCLEDELAY.
7.1.3.3.9.2 CSn: Chip-Select Signal Control Assertion/Deassertion Time (CSONTIME / CSRDOFFTIME /
CSWROFFTIME / CSEXTRADELAY)
The GPMC_CONFIG2_i[3-0] CSONTIME field defines the CSn signal-assertion time relative to the start
access time. It is common for read and write accesses.
275
SPRUH73H – October 2011 – Revised April 2013
Memory Subsystem
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