T8207 Datasheet, PDF (24/158 Pages) Agere Systems – ATM Interconnect

CelXpres T8207
ATM Interconnect
Advance Data Sheet
September 2001
6 Microprocessor Interface (continued)
6.3.1 Accessing the Extended Memory Registers
Before accessing the extended memory registers, the powerup sequence, as described in Section 3, Powerup/
Reset Sequence, must be completed. Accesses to extended memory are word accesses internally; therefore, the
least significant bit of the address is always ‘0.’ Only the most significant 25 bits are supplied to the extended mem-
ory address registers (addresses 30h—34h). The following procedure outlines the steps needed for extended
memory accesses in the T8207 device.
6.3.1.1 Extended Memory Writes
1. Write ext_a [25] bit to the extended memory address 4 register (little endian or big endian) (optional).
2. Write ext_a [24:17] byte to the extended memory address register 3 (little endian or big endian) (optional).
3. Write ext_a [16:9] byte to the extended memory address register 2 (little endian or big endian) (optional).
4. Write ext_a [8:6] bits to the extended memory address register 1 (little endian or big endian) (optional).
5. Write ext_d [15:8] byte to the extended memory data high register (little endian or big endian) (optional).
6. Write ext_d [7:0] byte to the extended memory data low register (little endian or big endian) (optional).
7. Write ext_a [5:1] bits; write “01,” “10,” or “11” to ext_we[1:0]; and write ‘1’ to ext_strt_acc in the extended mem-
ory access register (little endian or big endian) (mandatory).
8. Read the extended memory access register (little endian or big endian) to determine that the ext_strt_acc bit
has been cleared by hardware (mandatory).
6.3.1.2 Extended Memory Reads
1. Write ext_a [25] bit to the extended memory address 4 register (little endian or big endian) (optional).
2. Write ext_a [24:17] byte to the extended memory address register 3 (little endian or big endian) (optional).
3. Write ext_a [16:9] byte to the extended memory address register 2 (little endian or big endian) (optional).
4. Write ext_a [8:6] bits to the extended memory address register 1 (little endian or big endian) (optional).
5. Write ext_a [5:1] bits; write “00” to ext_we[1:0]; and write ‘1’ to ext_strt_acc in the extended memory access
register (little endian or big endian) (mandatory).
6. Read the extended memory access register (little endian or big endian) to determine that the ext_strt_acc bit
has been cleared by hardware (mandatory).
7. Read ext_d [15:8] byte from the extended memory data high register (little endian or big endian) (optional).
8. Read ext_d [7:0] byte from the extended memory data low register (little endian or big endian) (optional).
Note: Once the ext_strt_acc bit is set by software, only the extended memory access register should be
accessed until the ext_strt_acc bit is cleared by hardware.
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