emc646sp16ak Emlsi Inc., emc646sp16ak Datasheet - Page 17

• Manufacturer Part Number: emc646sp16ak
• Description: 4mx16 Bit Cellularram
• Manufacturer: Emlsi Inc.

Registers
Two user-accessible configuration registers define the device operation. The bus configuration register (BCR) defines how the Cellu-
larRAM interacts with the system memory bus and is nearly identical to its counterpart on burst mode Flash devices. The refresh
configuration register (RCR) is used to control how refresh is performed on the DRAM array. These registers are automatically loaded
with default settings during power-up, and can be updated any time the devices are operating in a standby state. A DIDR provides
information on the device manufacturer, CellularRAM generation, and the specific device configuration. The DIDR is read-only.
Access Using CRE
The registers can be accessed using either a synchronous or an asynchronous operation when the control register enable (CRE) input
is HIGH. (See Figure 10 through 13) When CRE is LOW, a READ or WRITE operation will access the memory array. The configuration
register values are written via addresses A[21:0]. In an asynchronous WRITE, the values are latched into the configuration register on
the rising edge of ADV#, CE#, or WE#, whichever occurs first; LB# and UB# are “Don’t Care”. The BCR is accessed when A[19:18]
are 10b; the RCR is accessed when A[19:18] are 00b. The DIDR is read when A[19:18] are 01b. For reads, address inputs other than
A[19:18] are “Don’t Care”, and register bits 15:0 are output on DQ[15:0]. Immediately after performing a configuration register READ or
WRITE operation, reading the memory array is highly recommended.
Figure 10: Configuration Register WRITE, Asynchronous Mode, Followed by READ ARRAY Operation
Note: 1. A[19:18] = 00b to load RCR, and 10b to load BCR.
(except A[19:18])
A[19:18]
LB#/UB#
DQ[15:0]
A[21:0]
ADV#
WE#
CRE
OE#
CE#
1
Select control register
OPCODE
t
AVS
t
Initiate control register access
AVS
t
VP
t
t
AVH
AVH
t
CW
Write address bus value
to control register
t
WP
17
t
CPH
Address
Address
EMC646SP16AK
Data Valid
4Mx16 CellularRAM
Don’t Care