DP8522AV-25 National Semiconductor, DP8522AV-25 Datasheet - Page 32

• Manufacturer Part Number: DP8522AV-25
• Description: IC CTRLR 4M VRAM 25MHZ 68PLCC
• Manufacturer: National Semiconductor

Specifications of DP8522AV-25

• Controller Type: Video RAM Controller, Drivers
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 68-LCC (J-Lead)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Supply: -
• Voltage - Supply: -
• Interface: -
• Other names: *DP8522AV-25

8 0 RAS and CAS Configuration Modes
The DP8520A 21A 22A allow the user to configure the
VRAM array to contain one two or four banks of VRAM
Depending on the functions used certain considerations
must be used when determining how to set up the VRAM
array Programming address bits C4 C5 and C6 along with
bank selects B0 –1 and CAS enables ECAS0–1 deter-
mine which RAS or group of RASs and which CAS or group
of CASs will be asserted during an access Different memo-
ry schemes are described The DP8520A 21A 22A is spec-
ified driving a heavy load of 72 VRAMs representing four
banks of VRAM with 16-bit words and 2 parity bits The
DP8520A 21A 22A can drive more than 72 VRAMs but the
AC timing must be increased Since the RAS and CAS out-
puts are configurable all RAS and CAS outputs should be
used for the maximum amount of drive
FIGURE 36 VRAM Array Setup for 16-Bit System (C6 C5 C4
32
37 The user can also configure the VRAM array into an 8
8 1 BYTE WRITING
By selecting a configuration in which all CAS outputs are
selected during an access each ECAS input enables a pair
of CAS outputs to select a byte in a word size of up to 16
bits In this case the RAS outputs are used to select which
of up to 4 banks is to be used as shown in Figures 36 and
bank system as shown in Figure 38 This setup can be used
along with byte writing for an 8-bit system if the LOW BYTE
and HIGH BYTE are connected to ECAS0 and ECAS1 re-
spectively The user can connect upper address bits to
ECAS0 1 for use in an 8 bank – 16-bit system but cannot
use byte writing in this case
e
1 1 0 during Programming)
TL F 9338 – 88