EMIF
The data macro is a bidirectional interface. It is used to transmit data from the memory controller to the
external memory chip during a write operation and receive data from memory and transmit it to the
memory controller during a read operation.
During a write operation, the data macro translates 32/16-bit words from memory controller to 8-bit words
and transmits them at double the bit rate to the memory along with the strobe. The strobe is center-
aligned to the data. Data can be prevented from writing to the memory using data mask signal.
During a read operation, the data macro receives 8-bit DDR data along with the strobe and converts it to
32/16- bit words and transmits them to the memory controller along with the read-valid signals.
7.3.3.3.3 Command Macro
It consists of PHY Command Macro, DLLs and the IOs integrated together. The command macro acts as
a unidirectional macro that transmits address and control bits from memory controller to the memory chip.
The clocks DDR_CLK and DDR_CLKn are used by the memory to register the command and address
transmitted on the transmit channels. All address and control signals are transmitted clock-centered with
respect to DDR_CLK and DDR_CLKn. The memory, on the positive edge of DDR_CLK and the negative
edge of DDR_CLKn, samples all address and control signals.
7.3.3.3.4 VTP Controller Macro
The VTP controller macro evaluates silicon performance at current voltage, temperature, and process
(VTP) to enable IO drivers to set constant predetermined output driver impedance. The controller operates
by comparing driver impedances to the external reference resistor and adjusting driver impedance to
obtain an impedance match. VTP Controller supports the following features:
•
The VTP controller generates information regarding the Voltage, temperature, and process(VTP) on a
chip to be shared with the device's IO drivers
•
Requires a Clock input from the core running at 20MHz or less
•
56 Clock cycles are needed to guarantee the VTP outputs are initially set after reset is removed
•
Can be used in static or dynamic update mode of operation
•
The VTP controller has internal noise filtering which allows it to control spurious update requests due
to noise
Impedance of the drivers and terminations must be updated often even while in operation. In such
scenarios where Voltage and Temperature are variables VTP macro can be configured in dynamic update
mode. In contrast, static mode of operation does not allow dynamic calibration of IO impedance, and
hence consumes lesser power compared to dynamic update mode.
It is possible that under noisy conditions, dynamic update controller can generate too frequent update
requests. Noise can cause the controller to request a change in the impedance that can again be quickly
reversed on subsequent clock cycles. To prevent the controller from making excessive numbers of
impedance changes, a digital filter is included which can be configured to regulate the update rate. For
example if the user configures the filter value as F2=0,F1=1 and F0=1, then an impedance update will be
performed only if four successive update requests are generated from the VTP controller. It is
recommended to use a filter value of 011'b.
shows the configuration details of the digital filter.
Table 7-98. Digital Filter Configuration
F2
F1
F0
Description
0
0
0
Off
0
0
1
Update on 2 consecutive update requests
0
1
0
Update on 3 consecutive update requests
0
1
1
Update on 4 consecutive update requests
1
0
0
Update on 5 consecutive update requests
1
0
1
Update on 6 consecutive update requests
1
1
0
Update on 7 consecutive update requests
408 Memory Subsystem
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated