TMS55166 datasheet(28/70 Pages) TI

28 / 70 page

TMS55165, TMS55166, TMS55175, TMS55176

262144 BY 16-BIT MULTIPORT VIDEO RAM

SMVS463 – DECEMBER 1995

POST OFFICE BOX 1443

• HOUSTON, TEXAS 77251–1443

split-register-transfer read

In split-register-transfer operations, the serial-data register is split into halves. The low half contains bits 0 – 127,

and the high half contains bits 128 – 255 (see Figure 20). While one half is being read out of the SAM port, the

other half can be loaded from the memory array.

512

× 512

Memory Array

256 - Bit

Data Register

255 256

511

255

A8 = 0

A8 = 1

Figure 20. Split-Register-Transfer Read

To invoke a split-register-transfer cycle, DSF is brought high, TRG is brought low, and both are latched at the

falling edge of RAS (see Figure 21). Nine row-address bits (A0 – A8) are also latched at the falling edge of RAS

to select one of the 512 rows available for the transfer. Eight of the nine column-address bits (A0 – A6 and A8)

are latched at the falling edge of CAS. Column-address bit A8 selects which half of the row is to be transferred.

Column-address bit A7 is ignored, and the split-register transfer is internally controlled to select the inactive half.

Column-address bits A0 – A6 select one of 127 tap points in the specified half of SAM. Locations 127 and 255

are not valid tap points in split-register-transfer operations. In stop-point mode, stop-point locations are not valid

tap points in split-register-transfer operations.

Full XFER

RAS

Split XFER

0511

A8 = 0

255

A7 = 0† 511

A8 = 1

255

A7 = 1† 511

A8 = 1

255

0 A7 = 0†

511

A8 = 0

255

DRAM

SAM

† A7 shown is internally controlled.

Figure 21. Example of a Split-Register-Transfer Read Operation

A full-register transfer must precede the first split-register transfer to ensure proper operation. After the

full-register transfer cycle, the first split-register transfer can follow immediately without any minimum SC clock

requirement (see Figure 22).

TMS55166 Datasheet(PDF) 28 Page - Texas Instruments

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