Datasheet

PIC18F97J60 FAMILY
DS39762F-page 222  2011 Microchip Technology Inc.
19.2 Ethernet Buffer and Register
Spaces
The Ethernet module uses three independent memory
spaces for its operations:
• An Ethernet RAM buffer which stores packet data
as it is received and being prepared for
transmission.
• A set of 8-bit Special Function Registers (SFRs),
used to control the module, and pass data back and
forth between the module and microcontroller core.
• A separate set of 16-bit PHY registers used
specifically for PHY control and status reporting.
The Ethernet buffer and PHY Control registers are
contained entirely within the Ethernet module and can-
not be accessed directly by the microcontroller. Data is
transferred between the Ethernet and microcontroller
by using buffer and pointer registers mapped in the
microcontroller’s SFR space. The relationships
between the SFRs and the Ethernet module’s memory
spaces are shown in Figure 19-4.
FIGURE 19-4: RELATIONSHIP BETWEEN MICROCONTROLLER AND ETHERNET
MEMORY SPACES
0000h
1FFFh
Ethernet Buffer
00h
1Fh
PHY Registers
Ethernet ModuleMicrocontroller SFRs
EDATA
ERDPT(H:L)
EWRPT(H:L)
ETXST(H:L)
ETXND(H:L)
ERXST(H:L)
ERXND(H:L)
ERXRDPT(H:L)
ERXWRPT(H:L)
MIRD(H:L)
MIWR(H:L)
MIREGADR
Ethernet Data
Buffer Address
PHY Register Data (In/Out)
PHY Register Address
Note: Microcontroller SFRs are not shown in the order of their placement in the data memory space. Memory areas are
not shown to scale.