Access PCI-DIO-24D(H) - Manual (Page 21)

Manual PCI-DIO-24DH 21
Counter/Timer Registers
Base + 10 Write/Read: Counter#A0 When writing, this register is used to load a count value into the
counter. The transfer is either a single or double byte transfer, depending on the control byte written to
the counter control register at BASE ADDRESS +13. If a double byte transfer is used, then the least-
significant byte of the 16 bit value is written first, followed by the most significant byte. When reading, the
current count of the counter is read. The type of transfer is also set by the control byte.
Base + 11 Write/Read: Counter #A1 See description for Base + 10 Write/Read.
Base + 12 Write/Read: Counter #A2 See description for Base + 10 Write/Read.
Base + 13 Write: Counter Control Register The control byte specifies the counter to be programmed, the
counter mode, the type of read/write operation, and the modulus. The control byte format is as follows:
These cards contain a type 8254 programmable counter/timer that allows you to implement such
functions as a Real Time Clock, Event Counter, Digital One-Shot, Programmable Rate Generator, Binary
Rate Multiplier, Complex Wave Generator and/or a Motor Controller. The 8254 consists of three, 16-bit,
presettable, down counters. Each counter can be programmed to any count between 1 or 2 and 65,535 in
binary format depending on the mode chosen.