TNETX3150 datasheet(47/78 Pages) TI

47 / 78 page

TNETX15AE

ADDRESS-LOOKUP DEVICE

SPWS041A – AUGUST 1997 – REVISED OCTOBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

DIO read cycle

The read-cycle waveforms are shown in Figure 15 and described in the following:

D The TNETX15AE host register address SAD1–SAD0 is asserted while SRNW is held high.

D After a setup time, ESCS goes low, initiating the read cycle.

D After a delay time, with ESCS low, SDATA7–SDATA0 is released from the high-impedance (Z) state.

SDATA7–SDATA0 is driven with valid data and SRDY goes low. The host can access the data.

D ESCS goes high (by the host) to signal completion of the cycle, causing SRDY to deassert. SRDY goes high

for one clock cycle before going into the Z state. SDATA7–SDATA0 also goes to the Z state.

ESCS

Host Address

SRNW

SAD1–SAD0

SDATA7–SDATA0

Data

SRDY

Figure 15. DIO Read-Cycle Waveforms

host (access) register space

The TNETX15AE registers, SRAM (internal and external), and EEPROM are indirectly accessed through the

access registers. The access registers are written/read to/through the DIO interface. There are four byte-wide

access registers. They are individually selected through the SAD bus, as shown in Table 7, and the registers

are read/written through the SDATA bus.

Table 7. DIO Access Register Code

SAD1

SAD0

ACCESS REGISTERS

DIO address low

DIO address high

DIO data

DIO data auto-increment

Two bytes, DIO address low and DIO address high, are used as a pointer to the address (DIOADR) of the internal

least-significant byte. The DIO address register is byte writeable. The user does not have to write to both DIO

address locations for each access to the internal registers. Up to 216 possible internal locations can be accessed

through the DIO address registers. Some of these first-level indirect registers are themselves address registers

(RAMaddr) for second-level indirect access to even bigger address spaces.

TNETX3150 Datasheet(PDF) 47 Page - Texas Instruments