Architecture
372
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
DDR2/mDDR Memory Controller
(1)
Legend: I = input, O = Output, Z = high impedance, pwr = power
DDR2/mDDR Memory Controller Signal Descriptions
Pin
Type
(1)
Description
DDR_CLK,
DDR_CLK
O/Z
Clock:
Differential clock outputs.
DDR_CKE
O/Z
Clock enable:
Active high.
DDR_CS
O/Z
Chip select:
Active low.
DDR_WE
O/Z
Write enable strobe:
Active low, command output.
DDR_RAS
O/Z
Row address strobe:
Active low, command output.
DDR_CAS
O/Z
Column address strobe:
Active low, command output.
DDR_DQM[1:0]
O/Z
Data mask
: Active high, output mask signal for write data.
DDR_DQS[1:0]
I/O/Z
Data strobe:
Active high, bi-directional signals. Output with write data, input with read data.
DDR_BA[2:0]
O/Z
Bank select:
Output, defining which bank a given command is applied.
DDR_A[13:0]
O/Z
Address:
Address bus.
DDR_D[15:0]
I/O/Z
Data:
Bi-directional data bus. Input for read data, output for write data.
DDR_DQGATE0
O/Z
Strobe Enable:
Active high.
DDR_DQGATE1
I/O/Z
Strobe Enable Delay:
Loopback signal for timing adjustment (DQS gating). Route from
DDR_DQGATE0 to DDR device and back to DDR_DQGATE1 with same constraints as used for
DDR clock and data.
DDR_ZP
I/O/Z
Output drive strength reference:
Reference output for drive strength calibration of N and P
channel outputs. Tie to ground via 50 ohm .5% tolerance 1/16th watt resistor (49.9 ohm .5%
tolerance is acceptable).
DDR_VREF
pwr
Voltage reference input:
Voltage reference input for the SSTL_18 I/O buffers. Note even in the
case of mDDR an external resistor divider connected to this pin is necessary.
14.2.3 Protocol Description(s)
The DDR2/mDDR memory controller supports the DDR2/mDDR SDRAM commands listed in
shows the signal truth table for the DDR2/mDDR SDRAM commands.
Table 14-1. DDR2/mDDR SDRAM Commands
Command
Function
ACTV
Activates the selected bank and row.
DCAB
Precharge all command. Deactivates (precharges) all banks.
DEAC
Precharge single command. Deactivates (precharges) a single bank.
DESEL
Device Deselect.
EMRS
Extended Mode Register set. Allows altering the contents of the mode register.
MRS
Mode register set. Allows altering the contents of the mode register.
NOP
No operation.
Power Down
Power-down mode.
READ
Inputs the starting column address and begins the read operation.
READ with
autoprecharge
Inputs the starting column address and begins the read operation. The read operation is followed by a
precharge.
REFR
Autorefresh cycle.
SLFREFR
Self-refresh mode.
WRT
Inputs the starting column address and begins the write operation.
WRT with
autoprecharge
Inputs the starting column address and begins the write operation. The write operation is followed by a
precharge.