I need to ask two things concerning IO_UPDATE.
- Edge sensitive or active high and consequences: In the datasheet, it reads:
- (Table 2. AC SPECIFICATIONS) IO_UPDATE Pin Setup Time to SYNC_CLK: 2ns, IO_UPDATE Pin Hold Time to SYNC_CLK: 0ns.
- (Table 5. Pin Function Descriptions) I/O_UPDATE Input/Output Update. Digital input (active high). A high on this pin transfers the contents of the I/O buffers to the corresponding internal registers.
Active high does not sound like edge sensitive to me. Still, under serial port programming, it reads:
- (SERIAL I/O PORT PIN DESCRIPTIONS) I/O_UPDATE — Input/Output Update The I/O update initiates the transfer of written data from the serial or parallel I/O port buffer to active registers.
I/O_UPDATE is active on the rising edge, and its pulse width must be greater than one SYNC_CLK period.
So my questions are:
- Is IO_UPDATE edge sensitive for operations other than serial port programming?
- Is it possible to set IO_UPDATE permanently high in order to get an output synchronous to SYNC_CLK?
- If b) is not possible, can I modulate IO_UPDATE with the same frequency as SYNC_CLK to have an output synchronous to SYNC_CLK or does IO_UPDATE have to be high for more than one SYNC_CLK period, same as for serial port programming?
2. Parallel port streaming and IO_UPDATE.
Datasheet: “To accommodate this functionality, the AD9914 provides a register control bit, parallel port streaming enable (0x00). When this bit is set to Logic 1, the parallel port operates without the need for an I/O update.”
My question here is:
- What does: "Without the need" mean? Is it still possible, during parallel port streaming, to use IO_UPDATE (I need to clear the phase accumulator somehow, and the autoclear phase accumulator functionality will just work with IO_UPDATE).
I would greatly appreciate any help from any side!