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Serial Channel registers
256
NS7520 Hardware Reference, Rev. D 03/2006
Register diagram and bit assignment
Serial Channel 1, 2 Receive Character Gap Timer
Address: FFD0 0018 / 58
The receive character gap timer closes out a receive serial data buffer due to a gap
between characters. The timer is reset when a character is received. When the timer
reaches its programmed threshold, the receive data buffer is closed.
Bits Access Mnemonic Reset Description
D31 R/W TRUN 0 Enable timer to run
Set to 1 to allow the receive buffer gap timer
to operate.
D30:15 N/A Reserved N/A N/A
D14:00 R/W BT 0 BT timer
The required value for the receive buffer gap
timer is a function of the channel bit-rate and
the maximum receive buffer size. It is
recommended that you set the buffer gap
timer to a value that is slightly larger that the
amount of time required to fill the maximum
buffer size using the channel bit-rate. Use this
equation to define the recommended buffer
gap timer value:
BT RECOMMENDED =
[(MAX_RX_BUF_SIZE * 1.10 * F
XTALE
) / (bit-
rate * 512)] - 1
If the resulting value doesn’t fit within the
range for BT, reconsider the size of
MAX_RF_BUF_SIZE.
Table 92: Serial Channel Receive Buffer Gap Timer bit definition
13121110987654321015 14
31 29 28 27 26 25 24 23 22 21 20 19 18 17 1630
Reserved
BT
TRUN
Rsvd