We have just completed work on a new fast counter feature in SPLat controllers. It is available in reFlashable MMi99s, SL99s and a recently completed custom controller. We call it "OnBoard Counter type A" (in case we in future come up with types B, C etc), or OBCA for short.
The OBCA gives you frequency counting at up to 18KHz, making it suitable for diesel engine speed measurement, belt speed (using a pulse encoder) and other pulse rate measurement applications.
The OBCA is fully documented in the SPLat Knowledge Base. Firmware upgrades with OBCA are available on our website, as is an update SPLat/PC V6.10.7 which supports the OBCA_ instructions.