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Электронный компонент: W134MH

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Direct RambusTM Clock Generator
W134M/W134S
Cypress Semiconductor Corporation
3901 North First Street
San Jose
CA 95134
408-943-2600
Document #: 38-07426 Rev. *A
Revised December 14, 2002
Features
Differential clock source for Direct RambusTM
memory
subsystem for up to 800-MHz data transfer rate
Provide synchronization flexibility: the Rambus
Chan-
nel can optionally be synchronous to an external sys-
tem or processor clock
Power managed output allows Rambus Channel clock
to be turned off to minimize power consumption for
mobile applications
Works with Cypress CY2210, W133, W158, W159, W161,
and W167 to support Intel
architecture platforms
Low-power CMOS design packaged in a 24-pin, 150-mil
SSOP package
Overview
The Cypress W134M/W134S provides the differential clock
signals for a Direct Rambus memory subsystem. It includes
signals to synchronize the Direct Rambus Channel clock to an
external system clock but can also be used in systems that do
not require synchronization of the Rambus clock.
Key Specifications
Supply Voltage: ..................................... V
DD
= 3.3V0.165V
Operating Temperature: .................................. 0C to +70C
Input Threshold: .................................................. 1.5V typical
Maximum Input Voltage: .........................................V
DD
+0.5V
Maximum Input Frequency: ..................................... 100 MHz
Output Duty Cycle: .................................. 40/60% worst case
Output Type: ........................... Rambus signaling level (RSL)
Block Diagram
Pin Configuration
PLL
Phase
PCLKM
MULT0:1
REFCLK
SYNCLKN
Output
Logic
Logic
Test
Alignment
STOPB
S0:1
CLK
CLKB
S0
S1
VDD
GND
CLK
NC
CLKB
GND
VDD
MULT0
MULT1
GND
24
23
22
21
20
19
18
17
16
15
14
13
VDDIR
REFCLK
VDD
GND
GND
PCLKM
SYNCLKN
GND
VDD
VDDIPD
STOPB
PWRDNB
1
2
3
4
5
6
7
8
9
10
11
12
W134M/W134S
Document #: 38-07426 Rev. *A
Page 2 of 13
Pin Definitions
Pin Name
Pin
No.
Pin
Type
Pin Description
REFCLK
2
I
Reference Clock Input: Reference clock input, normally supplied by a system
frequency synthesizer (Cypress W133).
PCLKM
6
I
Phase Detector Input: The phase difference between this signal and SYNCLKN
is used to synchronize the Rambus Channel Clock with the system clock. Both
PCLKM and SYNCLKN are provided by the Gear Ratio Logic in the memory con-
troller. If Gear Ratio Logic is not used, this pin would be connected to Ground.
SYNCLKN
7
I
Phase Detector Input: The phase difference between this signal and PCLKM is
used to synchronize the Rambus Channel Clock with the system clock. Both
PCLKM and SYNCLKN are provided by the Gear Ratio Logic in the memory con-
troller. If Gear Ratio Logic is not used, this pin would be connected to Ground.
STOPB
11
I
Clock Output Enable: When this input is driven to active LOW, it disables the
differential Rambus Channel clocks.
PWRDNB
12
I
Active LOW Power-Down: When this input is driven to active LOW, it disables the
differential Rambus Channel clocks and places the W134M/W134S in power-down
mode.
MULT 0:1
15, 14
I
PLL Multiplier Select: These inputs select the PLL prescaler and feedback divid-
ers to determine the multiply ratio for the PLL for the input REFCLK.
CLK, CLKB
20, 18
O
Complementary Output Clock: Differential Rambus Channel clock outputs.
S0, S1
24, 23
I
Mode Control Input: These inputs control the operating mode of the
W134M/W134S.
NC
19
-
No Connect
VDDIR
1
RefV
Reference for REFCLK: Voltage reference for input reference clock.
VDDIPD
10
RefV
Reference for Phase Detector: Voltage reference for phase detector inputs and
StopB.
VDD
3, 9, 16, 22
P
Power Connection: Power supply for core logic and output buffers. Connected to
3.3V supply.
GND
4, 5, 8, 13,
17, 21
G
Ground Connection: Connect all ground pins to the common system ground
plane.
MULT1
0
1
1
0
MULT0
0
0
1
1
W134M
PLL/REFCLK
4.5
6
8
5.333
W134S
PLL/REFCLK
4
6
8
5.333
S1
0
1
0
1
S0
0
0
1
1
MODE
Normal
Output Enable Test
Bypass
Test
W134M/W134S
Document #: 38-07426 Rev. *A
Page 3 of 13
DDLL System Architecture and Gear Ratio Log-
ic
Figure 1 shows the Distributed Delay Lock Loop (DDLL) sys-
tem architecture, including the main system clock source, the
Direct Rambus clock generator (DRCG), and the core logic
that contains the Rambus Access Cell (RAC), the Rambus
Memory Controller (RMC), and the Gear Ratio Logic. (This
diagram abstractly represents the differential clocks as a sin-
gle Busclk wire.)
The purpose of the DDLL is to frequency-lock and phase-align
the core logic and Rambus clocks (Pclk and Synclk) at the
RMC/RAC boundary in order to allow data transfers without
incurring additional latency. In the DDLL architecture, a PLL is
used to generate the desired Busclk frequency, while a distrib-
uted loop forms a DLL to align the phase of Pclk and Synclk at
the RMC/RAC boundary.
The main clock source drives the system clock (Pclk) to the
core logic, and also drives the reference clock (Refclk) to the
DRCG. For typical Intel architecture platforms, Refclk will be
half the CPU front side bus frequency. A PLL inside the DRCG
multiplies Refclk to generate the desired frequency for Busclk,
and Busclk is driven through a terminated transmission line
(Rambus Channel). At the mid-point of the channel, the RAC
senses Busclk using its own DLL for clock alignment, followed
by a fixed divide-by-4 that generates Synclk.
Pclk is the clock used in the memory controller (RMC) in the
core logic, and Synclk is the clock used at the core logic inter-
face of the RAC. The DDLL together with the Gear Ratio Logic
enables users to exchange data directly from the Pclk domain
to the Synclk domain without incurring additional latency for
synchronization. In general, Pclk and Synclk can be of differ-
ent frequencies, so the Gear Ratio Logic must select the ap-
propriate M and N dividers such that the frequencies of Pclk/M
and Synclk/N are equal. In one interesting example,
Pclk = 133 MHz, Synclk = 100 MHz, and M = 4 while N = 3,
giving Pclk/M = Synclk/N = 33 MHz. This example of the clock
waveforms with the Gear Ratio Logic is shown in Figure 2.
The output clocks from the Gear Ratio Logic, Pclk/M, and
Synclk/N, are output from the core logic and routed to the
DRCG Phase Detector inputs. The routing of Pclk/M and Syn-
clk/N must be matched in the core logic as well as on the
board.
After comparing the phase of Pclk/M vs. Synclk/N, the DRCG
Phase Detector drives a phase aligner that adjusts the phase
of the DRCG output clock, Busclk. Since everything else in the
distributed loop is fixed delay, adjusting Busclk adjusts the
phase of Synclk and thus the phase of Synclk/N. In this man-
ner the distributed loop adjusts the phase of Synclk/N to match
that of Pclk/M, nulling the phase error at the input of the DRCG
Phase Detector. When the clocks are aligned, data can be
exchanged directly from the Pclk domain to the Synclk do-
main.
Table 1 shows the combinations of Pclk and Busclk frequen-
cies of greatest interest, organized by Gear Ratio.
W134M/W134S
Refclk
W133
PLL
Phase
Align
D
4
DLL
RAC
RMC
M N
Gear
Ratio
Logic
Pclk
Busclk
Synclk
Pc
l
k
/
M
S
y
n
c
lk
/N
W158
W159
W161
W167
Figure 1. DDLL System Architecture
CY2210
Pclk
Synclk
Pclk/M =
Synclk/N
Figure 2. Gear Ratio Timing Diagram
W134M/W134S
Document #: 38-07426 Rev. *A
Page 4 of 13
Figure 3 shows more details of the DDLL system architecture,
including the DRCG output enable and bypass modes.
Phase Detector Signals
The DRCG Phase Detector receives two inputs from the core
logic, PclkM (Pclk/M) and SynclkN (Synclk/N). The M and N
dividers in the core logic are chosen so that the frequencies of
PclkM and SynclkN are identical. The Phase Detector detects
the phase difference between the two input clocks, and drives
the DRCG Phase Aligner to null the input phase error through
the distributed loop. When the loop is locked, the input phase
error between PclkM and SynclkN is within the specification
t
ERR,PD
given in Table 14 after the lock time given in the State
Transition Section.
The Phase Detector aligns the rising edge of PclkM to the
rising edge of SynclkN. The duty cycle of the phase detector
input clocks will be within the specification DC
IN,PD
given in
Table 13. Because the duty cycles of the two phase detector
input clocks will not necessarily be identical, the falling edges
of PclkM and SynclkN may not be aligned when the rising edg-
es are aligned.
The voltage levels of the PclkM and SynclkN signals are de-
termined by the controller. The pin VDDIPD is used as the
voltage reference for the phase detector inputs and should be
connected to the output voltage supply of the controller. In
some applications, the DRCG PLL output clock will be used
directly, by bypassing the Phase Aligner. If PclkM and SynclkN
are not used, those inputs must be grounded.
Selection Logic
Table 2 shows the logic for selecting the PLL prescaler and
feedback dividers to determine the multiply ratio for the PLL
from the input Refclk. Divider A sets the feedback and divider
B sets the prescaler, so the PLL output clock frequency is set
by: PLLclk=Refclk*A/B.
Table 3 shows the logic for enabling the clock outputs, using
the StopB input signal. When StopB is HIGH, the DRCG is in
its normal mode, and Clk and ClkB are complementary outputs
following the Phase Aligner output (PAclk). When StopB is
LOW, the DRCG is in the Clk Stop mode, the output clock
drivers are disabled (set to Hi-Z), and the Clk and ClkB settle
to the DC voltage V
X,STOP
as given in Table 14. The level of
V
X,STOP
is set by an external resistor network.
Table 1. Supported Pclk and Busclk Frequencies, by Gear Ratio
Gear Ratio and Busclk
Pclk
2.0
1.5
1.33
1.0
67 MHz
267 MHz
100 MHz
300 MHz
400 MHz
133 MHz
267 MHz
356 MHz
400 MHz
150 MHz
400 MHz
200 MHz
400 MHz
W134M/W134S
Refclk
W133
PLL
Phase
Align
D
4
DLL
RAC
RMC
M N
Gear
Ratio
Logic
Pclk
Busclk
Synclk
Pc
l
k
/
M
S
y
n
c
lk
/N
S0/S1 StopB
W158
W159
W161
W167
Figure 3. DDLL Including Details of DRCG
CY2210
Table 2. PLL Divider Selection
Mult0
Mult1
W134M
W134S
A
B
A
B
0
0
9
2
4
1
0
1
6
1
6
1
1
1
8
1
8
1
1
0
16
3
16
3
W134M/W134S
Document #: 38-07426 Rev. *A
Page 5 of 13
Table 4 shows the logic for selecting the Bypass and Test
modes. The select bits, S0 and S1, control the selection of
these modes. The Bypass mode brings out the full-speed PLL
output clock, bypassing the Phase Aligner. The Test mode
brings the Refclk input all the way to the output, bypassing
both the PLL and the Phase Aligner. In the Output Test mode
(OE), both the Clk and ClkB outputs are put into a high-imped-
ance state (Hi-Z). This can be used for component testing and
for board-level testing.
Table 5 shows the logic for selecting the Power-down mode,
using the PwrDnB input signal. PwrDnB is active LOW (en-
abled when 0). When PwrDnB is disabled, the DRCG is in its
normal mode. When PwrDnB is enabled, the DRCG is put into
a powered-off state, and the Clk and ClkB outputs are three-
stated.
Table of Frequencies and Gear Ratios
Table 6 shows several supported Pclk and Busclk frequencies,
the corresponding A and B dividers required in the DRCG PLL,
and the corresponding M and N dividers in the gear ratio logic.
The column Ratio gives the Gear Ratio as defined Pclk/Synclk
(same as M and N). The column F@PD gives the divided down
frequency (in MHz) at the Phase Detector, where
F@PD = Pclk/M = Synclk/N.
State Transitions
The clock source has three fundamental operating states. Fig-
ure 4
shows the state diagram with each transition labelled A
through H. Note that the clock source output may NOT be
glitch-free during state transitions.
Upon powering up the device, the device can enter any state,
depending on the settings of the control signals, PwrDnB and
StopB.
In Power-down mode, the clock source is powered down with
the control signal, PwrDnB, equal to 0. The control signals S0
and S1 must be stable before power is applied to the device,
and can only be changed in Power-down mode (PwrDnB = 0).
The reference inputs, V
DDR
and V
DDPD
, may remain on or may
be grounded during the Power-down mode.
Table 3. Clock Stop Mode Selection
Mode
StopB
Clk
ClkB
Normal
1
PAclk
PAclkB
Clk Stop
0
V
X,STOP
V
X,STOP
Table 4. Bypass and Test Mode Selection
Mode
S0
S1
Bypclk
(int.)
Clk
ClkB
Normal
0
0
Gnd
PAclk
PAclkB
Output Test (OE)
0
1
-
Hi-Z
Hi-Z
Bypass
1
0
PLLclk
PLLclk
PLLclkB
Test
1
1
Refclk
Refclk
RefclkB
Table 5. Power-down Mode Selection
Mode
PwrDnB
Clk
ClkB
Normal
1
PAclk
PAclkB
Power-down
0
GND
GND
Table 6. Examples of Frequencies, Dividers, and Gear Ratios
Pclk
Refclk
Busclk
Synclk
A
B
M
N
Ratio
F@PD
67
33
267
67
8
1
2
2
1.0
33
100
50
300
75
6
1
8
6
1.33
12.5
100
50
400
100
8
1
4
4
1.0
25
133
67
267
67
4
1
4
2
2.0
33
133
67
400
100
6
1
8
6
1.33
16.7
Test
M
N
L
K
Normal
Power-Down
Clk Stop
D
C
G
A
E
F
H
V
DD
Turn-On
V
DD
Turn-On
V
DD
Turn-On
V
DD
Turn-On
B
J
Figure 4. Clock Source State Diagram