Cypress Semiconductor FX2LP Información técnica descargar pdf (Pagina 414)

EZ-USB FX2 Technical Reference Manual

Page 15-94 EZ-USB FX2 Technical Reference Manual v2.1

If the flow state is such that the GPIF is the master on the bus (FLOWSTB.SLAVE = 0) then Mas-

ter Strobe will be one of the CTL[5:0] pins (see FLOWSTB). While in the flow state, if the flow logic

(see FLOWLOGIC) evaluates in such a way that Master Strobe should toggle (see

FLOWSTB.CTLTOGL), then this register defines the frequency at which it will toggle.

More precisely, this register defines the half period of the Master Strobe toggling frequency. Fur-

ther, to give the user a high degree of resolution this Master Strobe half period is defined in terms

of half IFCLK periods. Therefore, if IFCLK is running at 48 MHz, this gives a resolution of 10.8 nS.

Bits 7-0 D7:0 Master Strobe Half-Period

Number of half IFCLK periods that define the half period of Master Strobe (if it is a CTL pin).

Value must be at least 2, meaning that the minimum half period for Master Strobe is one full

IFCLK cycle.

For any transaction where the GPIF writes data onto FD[15:0], this register determines how long

the data is held. Valid choices are 0, ½ or 1 IFCLK cycle. This register applies to any data written

by the GPIF to FD[15:0], whether through a flow state or not.

For non-flow states, the hold amount is really just a delay of the normal (non-held) presentation of

FD[15:0] by the amount specified in HOLDTIME[1:0].

For flow states in which the GPIF is the master on the bus (FLOWSTB.SLAVE = 0), the hold

amount is with respect to the activating edge (see FLOW_MASTERSTB_EDGE) of Master Strobe

(which will be a CTL pin in this case).

For flow states in which the GPIF is the slave on the bus (FLOWSTB.SLAVE = 1), the hold amount

is really just a delay of the normal (non-held) presentation of FD[15:0] by the amount specified in

HOLDTIME[1:0] in reaction to the activating edge of Master Strobe (which will be a RDY pin in this

case). Note the hold amount is NOT directly with respect to the activating edge of Master Strobe in

FLOWSTBHPERIOD E6CD

b7 b6 b5 b4 b3 b2 b1 b0

D7 D6 D5 D4 D3 D2 D1 D0

RW RW RW RW RW RW RW RW

0 0 0 0 0 0 1 0

GPIFHOLDTIME E60C

b7 b6 b5 b4 b3 b2 b1 b0

0 0 0 0 0 0 HOLDTIME[1:0]

R R R R R R RW RW

0 0 0 0 0 0 0 0

1 2 ... 409 410 411 412 413 414 415 416 417 418 419 ... 459 460

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Cypress Semiconductor FX2LP Información técnica Pagina 414