NEC uPD72257, Preliminary User'S Manual

Page: 128 / 343

5.2.3.3 eeLong command
This command initiates data access in long (28-bit) addressing mode and defines
the access address ADD[27:0].
Byte 2nd byte 1st byte
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Content ADD[11:4] ADD[3:0] L[1:0] RW 1
Byte 4th byte 3rd byte
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Content ADD[27:20] ADD[19:12]
Parameters • bit1 = RW: defines the direction of the data transfer:
-
RW = 0: write mode, LBDIN[7:0] from Host CPU (HLBWR active)
- RW = 1: read mode, LBDIN[7:0] to Host CPU (HLBRD active)
• bit[3:2] = L[1:0]: defines the data length, i.e. the number of data bytes
to transfer:
-
L[1:0] = 00
B
: 1 data byte (8-bit data)
- L[1:0] = 01
B
: 2 data bytes (16-bit data)
- L[1:0] = 10
B
: 4 data bytes (32-bit data)
- L[1:0] = 11
B
: setting prohibited
• bit[31:4] = ADD[27:0]: 28-bit address
eeLong byte1 eeLong byte2 eeLong byte3
command
transfer
word
data transfer
L[1:0] = 00
B
L[1:0] = 01
B
L[1:0] = 10
B
eeLong byte4
data byte1 data byte2 data byte3 data byte4
eeLong byte1 eeLong byte2 eeLong byte3
command
transfer
eeLong byte4
halfword
data transfer
data byte1 data byte2
byte
data transfer
data byte
time
time
time
eeLong byte1 eeLong byte2 eeLong byte3
command
transfer
eeLong byte4
Figure 5-5 eeLong command flow
Chapter 5 Host CPU Interface
128
Preliminary User's Manual S19203EE1V3UM00