DP83916 Datasheet, PDF (50/96 Pages) National Semiconductor (TI) – SONICTM-16 Systems-Oriented Network Interface Controller

5 0 Bus Interface (Continued)
TABLE 5-1 Pin Description (Continued)
Symbol
Driver
Direction
Type
Description
SHARED-MEMORY ACCESS PINS
MREQ
I
Memory Request The system asserts this signal low when it attempts to access the
shared-buffer RAM The on-chip arbiter resolves accesses between the system and the
SONIC-16
Note Both CS and MREQ must not be asserted concurrently If these signals are
successively asserted there must be at least two bus clocks between the deasserting
edge of the first signal and the asserting edge of the second signal
SMACK
TP
O
Slave and Memory Acknowledge SONIC-16 asserts this dual function pin low in
response to either a Chip Select (CS) or a Memory Request (MREQ) when the SONIC-
16’s registers or it’s buffer memory is available for accessing This pin can be used for
enabling bus drivers for dual-bus systems
USER DEFINABLE PINS
USR0 1
TRI
I O Z User Define 0 1 These signals are inputs when SONIC-16 is hardware reset and are
outputs when SONIC-16 is a bus master (HLDA or BGACK) When hard reset (RST) is
low these signals input directly into bits 8 and 9 of the Data Configuration register
(DCR) respectively The levels on these pins are latched on the rising edge of RST
During busmaster operations (HLDA or BGACK is active) these pins are outputs whose
levels are programmable through bits 11 and 12 of the DCR respectively The USR0 1
pins should be pulled up to V_CC or pulled down to ground A 4 7 kX pull-up resistor is
recommended
POWER AND GROUND PINS
VCC1 – 5
Power The a5V power supply for the digital portions of the SONIC-16
TXVCC
RXVCC
PLLVCC
VCCL
Power These pins are the a5V power supply for the SONIC-16 ENDEC unit These
pins must be tied to V_CC even if the internal ENDEC is not used
GND1 – 6
Ground The ground reference for the digital portions of the SONIC-16
TXGND
ANGND
GNDL
Ground These pins are the ground references for the SONIC-16 ENDEC unit These
pins must be tied to ground even if the internal ENDEC is not used
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