TUSB5052 datasheet(66/84 Pages) TI

66 / 84 page

8–6

8.3

Mode-2/3: EPP and ECP Modes

These modes of operation support bidirectional data transfer per ECP and EPP protocols. In the output direction,

data/command written to PPDAT/PPADR are placed in the PPDAT register and are transmitted automatically using

ECP/EPP signaling. Typically, the MCU writes to PPADR to set the device address, and data transfer is done by the

DMA to PPDAT register. In the input direction, reverse-channel addressing is not supported. Only data input is

supported. Data input can be accomplished by either MCU or DMA transfer. The following describes the output and

input sequence:

8.3.1

DMA Output Sequence

MCU writes M[2:0] = 010b to PPMCR to set the port to mode-2.

MCU sets PPIMSK[ETxE] = 0 (no TxE interrupt).

MCU writes an address value to the PPADR register. This byte is placed into PD[7:0] and tagged as a

command byte.

MCU sets the proper DMA for output data transfer.

DMA reads a byte from buffer (in SRAM).

DMA writes the byte to the PPDAT register (TxE is used for DMA handshake).

Steps 5 and 6 are repeated without MCU involvement until either the full buffer has been transmitted, or an

error condition has been detected. ( A buffer size of up to 64 bytes can be transferred.)

When the full buffer has been transmitted, the DMA interrupts the MCU.

MCU checks for any error condition.

8.3.2

DMA Input Sequence

MCU writes M[2:0] = 010b to PPMCR to set the port to mode-2.

MCU sets PPIMSK[ERxF] = 0. (no RxF interrupt).

MCU sets the proper DMA for input data transfer.

DMA reads a byte from the PPDAT register (RxF is used for DMA handshake).

DMA writes the byte to buffer (in SRAM).

Steps 4 and 5 are repeated without MCU involvement until either the full buffer has been transmitted, or an

error condition has been detected. ( A buffer size of up to 64 bytes can be transferred)

When the full buffer has been received, the DMA interrupts the MCU.

MCU checks for any error condition.

TUSB5052 Datasheet(PDF) 66 Page - Texas Instruments