TM1100 Preliminary Data Book
Philips Semiconductors
11-2
PRELIMINARY INFORMATION
File: memsys.fm5, modified 7/24/99
11.3.1
SDRAM
TM1100 is designed to support synchronous DRAM
chips directly. SDRAM has a fast, synchronous interface
that permits burst transfers at a rate of one word per
clock cycle. The memory inside an SDRAM device is di-
vided into two banks, and the SDRAM implements inter-
leaved bank access to sustain maximum bandwidth.
SDRAM devices implement a power down mechanism
with self-refresh. TM1100’s power management takes
advantage of this mechanism.
TM1100 supports only Jedec-compatible SDRAM with
two internal banks of memory per device (
Note:
4
×512K×32 SDRAM with 4 internal banks is an excep-
11.3.2
SGRAM
Synchronous graphics DRAM (SGRAM) can also be
used in a TM1100 system. SGRAM has a 2
×128K×32 or-
ganization, and is essentially an SDRAM with some ad-
ditional features for raster graphics functions. The device
type is standardized by Jedec and offered by multiple
DRAM vendors. SGRAM devices are packaged in a 100-
pin QFP and are available in speed grades up to 133-
MHz.
By tying the DSF input of an SGRAM low, the device op-
erates like a standard 32-bit-wide SDRAM. Thus, tying
DSF low makes SGRAM compatible with TM1100’s
memory interface.
11.4
MEMORY GRANULARITY AND SIZES
TM1100 supports a variety of memory sizes thanks to:
The availability of many organizations of SDRAM
devices, and
TM1100’s support for up to four memory ranks.
The minimum memory size is 512KB using two
2
×64K×16 SDRAM parts on the 32-bit data bus.
Up to four memory devices can be connected to TM1100
without any glue logic and without sacrificing any perfor-
mance. The maximum memory size with full perfor-
mance is 16MB using two 4
×512K×32 SDRAMs on a 32-
bit data bus.
Larger memories can be constructed using more devic-
es, but the frequency of the memory interface must be
lowered to account for the extra propagation delay due to
the excessive loading on the interface signals (see
Sec-number of chips is connected (more than 16), it is advan-
tageous to add external buffers to the address and con-
trol signals.
The following rules apply to memory rank design:
All devices in a rank must be of the same type.
All ranks must be a power of two in size.
All ranks must be equal size.
Table 11-3 lists some example memory system designs.
Note that the 64-MB configuration requires external buff-
ers. Note:
Some of these congurations may not be economi-
cally attractive due to the price premium for small-
capacity devices.
“Max. MHz” refers to the memory interface/SDRAM
speed, not the TM1100 core operating frequency.
11.5
MEMORY SYSTEM PROGRAMMING
Memory system parameters are determined by the con-
tents of two configuration registers, MM_CONFIG and
these registers, and
Figure 11-2 shows their formats. To
ensure compatibility with future devices, any undefined
MMIO bits should be ignored when read.
MM_CONFIG and PLL_RATIOS are loaded from the
ory interface is held in reset state. After the memory in-
terface is released from reset, the contents of these reg-
isters cannot be altered.
These registers are visible in MMIO space. They can be
read, but writes have no effect.
Figure 11-1. TM1100 provides a high-performance memory interface for local main memory. The interface
connects the internal highway bus to external SDRAM or SGRAM. The interface is glueless for an array of
up to four devices.
TM1100
Memory
Interface
Chip Selects#
Address,
Clock Enables,
RAS#, CAS#, WE#
Byte Enables[3:0]
Clock
MatchOut
MatchIn
Data[31:0]
CS#
Address, Control
DQM[3:0]
CLK
DQ[31:0]
GND
Propagation Delay
Compensation Loop
22
0
SDRAM
Memory
Array
Data
Highway
TM1100
On-Chip
Peripherals
DSPCPU
0 pf