1. A method for adjusting a transmission rate of Intersystem Channel (ISC) words from a Generic Framing Procedure (GFP) data mapping device having a FIFO buffer and a transceiver operably coupled to the FIFO buffer, comprising: reading first and second ISC words from the FIFO buffer that were received from a transmitting device; determining whether a first number of ISC words stored in the FIFO buffer is greater than a second predetermined number indicating an over-running condition; determining whether the first and second ISC words indicate either an ISC continuous sequence of words or an ISC idle sequence of words only if the first number of ISC words is greater than the second predetermined number; deleting the first and second ISC words only if the first and second ISC words indicate either the ISC continuous sequence of words or the ISC idle sequence of words, and the first number of ISC words is greater than the second predetermined number indicating the over-running condition; and reading a third ISC word from the FIFO buffer and transmitting the third ISC word from the transceiver.
5. The method of claim 1 , further comprising: determining whether the first number of ISC words stored in the FIFO buffer is less than a third predetermined number indicating an under-running condition; determining whether the first and second ISC words indicate an ISC idle sequence of words, if the first number is less than the third predetermined number; and transmitting third and fourth ISC idle words from the transceiver if the first and second ISC words indicate the ISC idle sequence of words.