I'm sending a 16-bit data word from the PIC 16f877A to the AD667, only this data is in the Timer1 register wich we can have access to from one pin , and i really don't know how to send it to the DAC
If you only use one device, you can directly connect the /CS pin to your microcontroller.
Can you check AD5330, that's a newer 8-bit, parallel interface DAC.
Just to clarify, do you intend to display the 16-bit counter/timer into analog form using AD667? If yes, then since AD667 is using a parallel interface, you should convert the 16-bit register into a parallel form so that each GPIO pin will handle 1-bit. So definitely data [DB11:DB0] should be connected to the microcontroller. /CS, lines [A3:A0] should also be connected depending on the timing performance/sequence you want to achieve, but you can short them all to GND to enable all latches to test if your device works as intended.
AD667 is a 12-bit DAC and your data is 16 bits so effectively the system is still 12 bits, we have other DACs in our portfolio which has 16-bit DAC registers. If you really just want to display your 16-bit counter into analog form, there are other couple of ways, I am not sure if using a DAC would be the best option considering different factors such as speed.