The counter can be configured to operate as a 1, 2, 3 or 4-byte counter. When configured as a n-byte counter, the CNTR, DTR and OTR are all configured as n-byte registers, where n = 1, 2, 3 or 4. The content of the instruction/data identity is automatically adjusted to match the n-byte configuration. For example, if the counter is configured as a 2-byte counter, the instruction "write to DTR" expects 2 data bytes following the instruction byte. If the counter is configured as a 3-byte counter, the same instruction will expect 3 bytes of data following the instruction byte. Following the transfer of the appropriate number of bytes any further attempt of data transfer is ignored until a new instruction cycle is started by switching the SS/ input to high and then low. The counter can be programmed to operate in a number of different modes, with the operating characteristics being written into the two mode registers MDR0 and MDR1. Hardware I/Os are provided for event driven operations, such as processor interrupt and index related functions.