
TM1100 Preliminary Data Book
Philips Semiconductors
11-4
PRELIMINARY INFORMATION
File: memsys.fm5, modified 7/24/99
TM1100’s core logic. The default value is one, which
causes the TM1100 core to be clocked by the input of the
CPU PLL (i.e., the memory interface clock). A value of
zero causes normal operation, and the core is clocked by
the output of the CPU PLL.
Note that if both CB and SB are set to one (bypass the
CPU PLL and bypass the SDRAM PLL), TM1100’s core
logic is effectively clocked at the external input frequen-
cy.
Note: it is illegal to use the output of a disabled PLL. For
example, it is illegal to have CD set to one while CB is set
to zero.
SD (SDRAM PLL Disable). The one-bit SD field deter-
mines whether or not the SDRAM PLL is turned on. The
default value is one, which disables the SDRAM PLL,
and it dissipates almost no power. For normal operation
the value should be zero, enabling the SDRAM PLL.
SB (SDRAM PLL Bypass). The one-bit SB field deter-
mines whether the input or the output of the SDRAM PLL
drives the memory interface and memory devices. The
default value is one, which causes the memory system to
be clocked by the input of the SDRAM PLL (TM1100’s
external input clock). A value of zero causes normal op-
eration, and the memory system is clocked by the output
of the SDRAM PLL.
11.6
MEMORY INTERFACE PIN LIST
The memory interface consists of 61 signal pins includ-
ing clocks (but excluding power and ground pins).
11.7
ADDRESS MAPPING
Table 11-8 shows how internal address bits from the
data highway bus (which connects all internal TM1100
units) are mapped to main-memory address-bus pins
(MM_A[11:0]). The mapping is determined by the state of
the rank-size bits in the MM_CONFIG register.
The column “Rank Addr./H.Way Bits” specifies which in-
ternal data-highway address bits select the preliminary
SDRAM rank. The actual rank used is subject to the lim-
itation implied by the relationship between SDRAM aper-
Table 11-5. MM_CONFIG Fields
Field
Function
REFRESH
Refresh interval in memory clock cycles.
Default value 1000 (0x03E8).
SIZE
Memory rank size
0
Reserved
1
512KB
2
1MB
3
2MB
4
4MB
5
8MB
6
16MB
7
Reserved
Table 11-6. PLL_RATIOS Fields
Field
Function
CR
CPU:memory ratio
0
1:1
1
2:1
2
3:2
3
4:3
4
5:4
5–7 Reserved
SR
Memory:external ratio
0
2:1
1
3:1
CD
CPU PLL Disable
0
CPU PLL on
1
CPU PLL off
CB
CPU PLL bypass
0
CPU
←PLL
1
CPU
←Memory
SD
SDRAM PLL Disable
0
SDRAM PLL on
1
SDRAM PLL off
SB
SDRAM PLL bypass
0
Memory
←PLL
1
Memory
←external
Figure 11-3. TM1100 memory and core PLL connections.
Memory System
PLL
DSPCPU PLL
CR
0
42
3
75
6
SD SB CD CB SR
PLL_RATIOS Register
TM1100
Core
Clock
TM1100
TRI_CLKIN
MM_CLK1
MM_CLK0
External Clock Input
Memory System Clocks