PSD835G2-90U STMicroelectronics, PSD835G2-90U Datasheet - Page 70

• Manufacturer Part Number: PSD835G2-90U
• Description: IC FLASH 4MBIT 90NS 80TQFP
• Manufacturer: STMicroelectronics

Specifications of PSD835G2-90U

• Format - Memory: FLASH
• Memory Type: FLASH
• Memory Size: 4M (512K x 8)
• Speed: 90ns
• Interface: Parallel
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 80-TQFP, 80-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-2015

MCU bus interface
16.5
Table 12.
70/120
Configuration
1
2
3
4
80C251
The Intel 80C251 MCU features a user-configurable bus interface with four possible bus
configurations, as shown in
The first configuration is 80C31 compatible, and the bus interface to the PSD is identical to
that shown in
as shown in
PSD. The A16 connection to PA0 allows for a larger address input to the PSD. The fourth
configuration is shown in
Select Enable (PSEN) is connected to CNTL2.
The 80C251 has two major operating modes: Page mode and Non-page mode. In Non-
page mode, the data is multiplexed with the lower address byte, and Address Strobe
(ALE/AS, PD0) is active in every bus cycle. In Page mode, data (D7-D0) is multiplexed with
address (A15-A8). In a bus cycle where there is a Page hit, Address Strobe (ALE/AS, PD0)
is not active and only addresses (A7-A0) are changing. The PSD supports both modes. In
Page mode, the PSD bus timing is identical to Non-Page mode except the address hold time
and setup time with respect to Address Strobe (ALE/AS, PD0) is not required. The PSD
access time is measured from address (A7-A0) valid to data in valid.
80C251 configurations
80C251 READ/WRITE
PSEN only
PSEN only
Table
PSEN
PSEN
pins
Figure
WR
WR
WR
WR
RD
RD
13. There is only one Read Strobe (PSEN) connected to CNTL1 on the
21. The second and third configurations have the same bus connection
Figure
Table
22. Read Strobe (RD) is connected to CNTL1 and Program
Connecting to PSD pins
12.
CNTL0
CNTL1
CNTL2
CNTL0
CNTL1
CNTL0
CNTL1
CNTL0
CNTL1
CNTL2
Non-Page mode, 80C31
compatible A7-A0 multiplex with
D7-D0
Non-Page mode
A7-A0 multiplex with D7-D0
Page mode
A15-A8 multiplex with D7-D0
Page mode
A15-A8 multiplex with D7-D0
Page mode
PSD835G2