feat(arnitech): network entries NET_INIT, NET_MAC, NET_SEND, NET_RECV at $FF0C-$FF15

Version 2 of the Arnitech jump table, with 6 entries: whole Ethernet frames
through the CS8900A at the RR-Net socket (arnitech's ADR 0027), found by its
Product ID and polled, from the CS8900A datasheet's PacketPage registers and
its 8-bit mode. NET_INIT resets the chip and turns on receiving its own and
broadcast frames and sending; NET_MAC copies the Individual Address; NET_SEND
bids and writes a frame; NET_RECV copies the oldest frame received, or drops
one longer than the buffer with Skip_1. Carry is the result, with an error
code in A, and the pointer and count go in SAL and EAL.

src/kernal/arnitech/ff00.arnitech_jumptable.s

@@ -9,11 +9,12 @@
 ; stay clear, for the stock IRQ entry, CINT, and the KERNAL revision byte.
 ;
 ; $FF00-$FF03  "ARNI"
-; $FF04        version of the table, $01
+; $FF04        version of the table, $02
 ; $FF05        number of entries
 ;
 ; $FF06  ARNI_FINDCARD - finds the first Card slot holding a Card of a given type
-;        In:  A = the Card's type ($01 Redstone Card, $02 Internet Card; $00 finds an empty slot)
+;        In:  A = the Card's type ($01 Redstone Card, $02 Internet Card, $03 Network Card;
+;             $00 finds an empty slot)
 ;        Out: carry clear if found: A = the slot (0-5), X = the low byte of its Card window
 ;             ($DEA0 + 16 * slot, so LDA $DE00,X reads the window's first byte);
 ;             carry set if no slot holds one, or no controller answers (a Cartridge switched it off)
@@ -26,15 +27,50 @@
 ;             untouched but on 50 Hz all the same
 ;        A and X are not kept, Y is
 ;
+; Version 2 adds the network: whole Ethernet frames, from the Destination Address to the end of
+; the data without the CRC, through the CS8900A at the RR-Net socket (arnitech's ADR 0027),
+; found by its Product ID. Software polls; ARP and IP are its own.
+;
+; $FF0C  NET_INIT - resets the chip and sets it to receive frames for its own address and
+;        broadcasts, and to send
+;        In:  nothing
+;        Out: carry clear if done; carry set if there is no Network Card
+;        A and X are not kept, Y is
+;
+; $FF0F  NET_MAC - copies the MAC address: the chip's Individual Address, which a reset sets to
+;        the Network Card's
+;        In:  X/Y = the address of 6 bytes for it, low byte in X
+;        Out: carry clear if copied; carry set if there is no Network Card
+;        A, X, and Y are not kept
+;
+; $FF12  NET_SEND - sends a frame
+;        In:  A = a zero page address holding a pointer to the frame,
+;             X/Y = its length, 14-1514, low byte in X; the chip pads one under 60 bytes
+;        Out: carry clear if sent; carry set if not, with A = 1 no Network Card, 2 no room in
+;             the chip while it holds frames received, 3 the chip refuses the length
+;        A, X, and Y are not kept
+;
+; $FF15  NET_RECV - takes the oldest frame received
+;        In:  A = a zero page address holding a pointer to a buffer,
+;             X/Y = its length, low byte in X
+;        Out: carry clear if a frame was copied into the buffer, with X/Y = its length, low byte
+;             in X; carry set if not, with A = 0 none waiting, 1 no Network Card, 4 the frame is
+;             longer than the buffer, and is dropped
+;        A is not kept when a frame is copied
+;
 
 !ifdef CONFIG_ARNITECH_CONTROLLER {
 
 arnitech_jumptable:
 
 	!byte $41, $52, $4E, $49           ; "ARNI"
-	!byte $01                          ; version
-	!byte $02                          ; entries
+	!byte $02                          ; version
+	!byte $06                          ; entries
 
 	jmp arnitech_find_card             ; $FF06
 	jmp arnitech_set_tod               ; $FF09
+	jmp arnitech_net_init              ; $FF0C
+	jmp arnitech_net_mac               ; $FF0F
+	jmp arnitech_net_send              ; $FF12
+	jmp arnitech_net_recv              ; $FF15
 }