Here is a list of the tercios/regiments of the Spanish army which besieged the castle of Salses in Rousillon the winter of 1639 to 1640. More than the 40% of the soldiers (about 13.000) were Catalan recruits. The first 9 units were levied and paid by the Generalitat, the city hall of Barcelona, and the nobility of the country. Other units included Castilian, Aragonese, Valencian, Italian, Walloon and Irish soldiers. The castle, in French hands since july, was retaken, but a heavy cost: 10.000 men died, mostly from illnes.
COPIA AVTENTICA DE LA GENTE QUE TIENE
su Magestad en el Principado de Cathaluña, contra
Something that draws considerable attention is that some regiments had just a few dozens of musketeers, while others had few or no arquebusiers (the Irish tercio, specifically). Sadly, I don't know the reason. The best equiped tercio, on the other hand, is that of Barcelona (under Josep de Sorribes, former cavalry captain in the Army of Flanders). I hope to get soon a good relation of the cavalry.
Source: Relacion Verdadera de Todo lo Sucedido en los Condados de Rosellon y Cerdaña, desde los primeros de Iunio, que entrò el enemigo por aquel principado, hasta diez y nueve de Setiembre, que se dio la batalla al Frâces, en la qual queò desbaratado. (Universidad de Sevilla) [Link]