
Data Sheet
June 2001
DSP16410B Digital Signal Processor
Agere Systems Inc.
Agere Systems—Proprietary
Use pursuant to Company instructions
101
4 Hardware Architecture
(continued)
4.14 System and External Memory Interface (SEMI)
(continued)
4.14.1 External Interface
(continued)
4.14.1.1 Configuration
The SEMI configuration pins are inputs that are individually tied high or low based on system requirements. The
ESIZE and ERTYPE pins reflect the configuration of the external memory system. The EXM pin specifies the
memory boot area for the DSP16000 cores.
Table 52
details the SEMI configuration pins.
Table 52. Configuration Pins for the SEMI External Interface
F
Pin
ESIZE
(input)
Value
0
Description
Configures external data bus as 16 bits:
ED[31:16] is active, and ED[15:0] is 3-state.
EA[18:0] provides the address.
For a single-word (16-bit) access, the SEMI places the address onto EA[18:0]:
— For a read, the SEMI transfers the word from ED[31:16].
— For a write, the SEMI drives the word onto ED[31:16] and asserts ERWN0.
For a double-word (32-bit) access, the SEMI performs two single-word (16-bit) accesses:
— First, the SEMI accesses the most significant half of the double word at the original address (see single-
word (16-bit) access described above).
— Second, the SEMI increments the address and accesses the least significant half of the double word
(see single-word (16-bit) access described above).
Configures external data bus as 32 bits:
1
EA[18:1] provides the even address.
For a single-word (16-bit) access to an even location:
— For a read, the SEMI transfers the word from ED[31:16] and ignores ED[15:0].
— For a write, the SEMI drives the word onto ED[31:16] and asserts ERWN0
.
For a single-word (16-bit) access to an odd location:
— For a read, the SEMI transfers the word from ED[15:0] and ignores ED[31:16].
— For a write, the SEMI drives the word onto ED[15:0] asserts ERWN1
.
For a double-word (32-bit) aligned access, i.e., an access to an even address:
— For a read, the SEMI transfers the double word from ED[31:0].
— For a write, the SEMI drives the double word onto ED[31:0] and asserts ERWN0 and ERWN1
.
For a double-word (32-bit) misaligned access, the SEMI performs two single-word (16-bit) accesses:
— First, the SEMI accesses the most significant half of the double word at the original address (see single-
word (16-bit) access to an odd location described above).
— Second, the SEMI increments the address and accesses the least significant half of the double word
(see single-word (16-bit) access to an even location described above).
The EROM component is populated with ROM or asynchronous SRAM, and the SEMI performs asynchro-
nous accesses to the EROM component.
The EROM component is populated with synchronous ZBTSRAM, and the SEMI performs synchronous
accesses to the EROM component.
If EXM is logic low when the RSTN pin makes a low-to-high transition, both cores begin program execution
from their internal ROM (IROM) memory at location 0x20000.
If EXM is logic high when the RSTN pin makes a low-to-high transition, both cores begin program execution
from external ROM (EROM) memory at location 0x80000. The SEMI arbitrates the accesses from the two
cores.
For a synchronous write, the SEMI also asserts EA0 as a write strobe. The EROM component is synchronous if the ERTYPE pin is logic high. The
ERAM component is synchronous if the YTYPE field (
ECON1
[9]) is set. The EIO component is synchronous if the ITYPE field (
ECON1
[10]) is
set.
ECON1
is described in
Table 60 on page 110
.
ERTYPE
(input)
0
1
EXM
(input)
0
1