Datasheet

DS21Q50
17 of 87
Signal Name:
PBTS
Signal Description:
Parallel Bus Type Select
Signal Type:
Input
Used to select between Motorola and Intel parallel bus types.
Signal Name:
AD0 to AD7/SDO
Signal Description:
Data Bus or Address/Data Bus [D0 to D6]
Data Bus or Address/Data Bus [D7]/Serial Port Output
Signal Type:
Input/Output
In nonmultiplexed bus operation (MUX = 0), serves as the data bus. In multiplexed bus operation
(MUX = 1), serves as an 8-bit multiplexed address/data bus.
Signal Name:
A0 to A4
Signal Description:
Address Bus
Signal Type:
Input
In nonmultiplexed bus operation, this serves as the address bus. In multiplexed bus operation, these pins are not
used and should be wired low.
Signal Name:
RD(DS)/SCLK
Signal Description:
Read Input—Data Strobe/Serial Port Clock
Signal Type:
Input
RD and DS are active-low signals. DS active HIGH when in multiplexed mode. See bus-timing diagrams.
Signal Name:
CS
Signal Description:
Chip Select
Signal Type:
Input
Must be low to read or write to the device. CS is an active low signal.
Signal Name:
ALE (AS)/A5
Signal Description:
Address Latch Enable (Address Strobe) or A6
Signal Type:
Input
In nonmultiplexed bus operation, this serves as the upper address bit. In multiplexed bus operation, this serves to
demultiplex the bus on a positive-going edge.
Signal Name:
WR (R/W)/SDI
Signal Description:
Write Input (Read/Write)/Serial Port Data Input
Signal Type:
Input
WR is an active-low signal.
2.1.5 Serial Port Control Pins
Signal Name:
SDO
Signal Description:
Serial Port Output
Signal Type:
Output
Data at this output can be updated on the rising or falling edge of SCLK.
Signal Name:
SDI
Signal Description:
Serial Port Data Input
Signal Type:
Input
Data at this input can be sampled on the rising or falling edge of SCLK.