MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
1211
Preliminary—Subject to Change Without Notice
Figure 26-43. TX FIFO Pointers and Counter
26.6.4.1
Address Calculation for the First-in Entry and Last-in Entry in the TX
FIFO
The memory address of the first-in entry in the TX FIFO is computed by the following equation:
Eqn. 26-7
The memory address of the last-in entry in the TX FIFO is computed by the following equation:
Eqn. 26-8
TX FIFO Base - Base address of TX FIFO
TXCTR - TX FIFO Counter
TXNXTPTR - Transmit Next Pointer
TX FIFO Depth - Transmit FIFO depth, implementation specific
26.6.4.2
Address Calculation for the First-in Entry and Last-in Entry in the RX
FIFO
The memory address of the first-in entry in the RX FIFO is computed by the following equation:
Eqn. 26-9
The memory address of the last-in entry in the RX FIFO is computed by the following equation:
Eqn. 26-10
-
-
Entry A (first in)
Entry B
Entry C
Entry D (last in)
-
-
Push TX FIFO Register
Transmit Next
Data Pointer
Shift Register
SOUT
+1
-1
TX FIFO Counter
TX FIFO Base
First-in Entry Address
TX FIFO Base
4
TXNXTPTR
×
(
)
+
=
Last-in Entry address
TX FIFO Base
4
modulo TX FIFO depth TXCTR
TXNXTPTR
1
–
+
(
)
×
+
=
First-in Entry Address
RX FIFO Base
4
POPNXTPTR
×
(
)
+
=
Last-in Entry address
RX FIFO Base
4
modulo RX FIFO depth RXCTR
POPNXTPTR
1
–
+
(
)
×
+
=